Piezoelectric/electrostrictive device

ABSTRACT

A piezoelectric/electrostrictive device that includes a base  11  having a pair of right and left movable parts  11   a,    11   b  and a fixing part  11   c  disposed at one end thereof as well as piezoelectric/electrostrictive elements  12   a,    12   b  disposed on the sides of the movable parts  11   a,    11   b  of the base  11  is fabricated to have a construction with fewer components. The piezoelectric/electrostrictive device having a construction with fewer components is provided by adopting a base  11  having an integral structure formed by bending an original plate stamped into a shape that delineates a plane development of the base, as the base of the piezoelectric/electrostrictive device. In addition, in this piezoelectric/electrostrictive device, piezoelectric/electrostrictive elements are arranged on inner sides of a pair of left and right movable parts. Accordingly, destruction of the piezoelectric/electrostrictive element can hardly occur and high reliability of the piezoelectric/electrostrictive device is achieved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric/electrostrictivedevice.

2. Description of the Background Art

As one form of piezoelectric/electrostrictive device, there are known apiezoelectric/electrostrictive device of a form that includes a basehaving a pair of right and left movable parts and a fixing part thatconnects the movable parts with each other at one end thereof as well asa piezoelectric/electrostrictive element disposed on at least one sideof the movable parts of the base, and a piezoelectric/electrostrictivedevice of a form that includes a base having a pair of right and leftmovable parts, a fixing part that connects the movable parts with eachother at one end thereof, and a mounting part that connects the movableparts with each other at the other end thereof as well as apiezoelectric/electrostrictive element disposed on at least one side ofthe movable parts of the base, as disclosed in the specification ofEuropean Patent EP1017116A2.

The piezoelectric/electrostrictive device of such a form has a functionof operating the movable parts caused by the displacement operation ofthe piezoelectric/electrostrictive element or a sensing function ofsensing the displacement of the movable parts input from the side thatis sensed, with the use of the piezoelectric/electrostrictive element.By effectively using these functions, the piezoelectric/electrostrictivedevice is used in a wide range of fields such as described below.

Namely, the piezoelectric/electrostrictive devices of such a form areused as active elements such as various transducers, various actuators,frequency region functional components (filters), transformers,vibrators and resonators for communication or mechanical power,oscillators, and discriminators, various sensor elements such assupersonic wave sensors, acceleration sensors, angular velocity sensors,impact sensors, and mass sensors, and various actuators that are put touse for displacement, positioning adjustment, and angle adjustmentmechanism for various precision components of optical instruments andprecision apparatus.

Meanwhile, the piezoelectric/electrostrictive device of such a form isformed typically by cutting a device master into a suitable size, andthe device master is constructed by bonding apiezoelectric/electrostrictive element onto both of the front and rearsurfaces of a base master via an adhesive, or is constructed byintegrally forming these. Here, the base master is constructed bylaminating and baking plural sheets.

Thus, the piezoelectric/electrostrictive device having such a form has alarge number of construction components, so that the device is producedat a high cost and through a cumbersome assembling work. Moreover, sincethe construction components are bonded via an adhesive, there arises avariation of adhesion between the construction components, giving riseto a fear that the device characteristics may be adversely affected.

Further, the piezoelectric/electrostrictive device having such a form isproduced by adopting means to cut a device master suitably into a largenumber of devices. Therefore, the piezoelectric/electrostrictive devicesformed by cutting are contaminated with dusts generated at the time ofcutting, cutting liquid, and organic components such as an adhesive orwax used for holding the device master at the time of cutting, so thatit is not easy to clean the piezoelectric/electrostrictive device.

Also, in the case where the base is constructed with ceramics, one mustadopt a hard ceramic material such as zirconia, since the ceramics areliable to be split. Even if a hard ceramic material is adopted, one mustchoose a suitable cutting condition so as not to generate loss of thematerial or cracks. Further, since the base is made of a hard ceramicmaterial, the machining process is difficult to be designed and, inorder to increase the number of machining products, one must give acareful consideration such as use of a large number of machiningapparatus having different functions.

The base can be constructed with a metal material; however, the metalmaterial gives rise to an oxidized end surface by friction heat duringthe cutting process and burrs remained on the processed end surface, sothat one must add another step of removing these. Further, thepiezoelectric/electrostrictive device can be tested only after thedevice master is cut.

Meanwhile, the device cut out from the device master is preferablycleaned by adopting supersonic wave cleaning that can easily remove thecontamination. However, if a strong supersonic wave is used to obtain ahigh cleaning effect in supersonic wave cleaning, the device may bedamaged, and the piezoelectric/electrostrictive element may be broken orpeeled off from the base. For this reason, if the supersonic wavecleaning is adopted, one must select a weak supersonic wave that doesnot give damages to the device. However, if such a cleaning condition isadopted, a long period of time is needed in removing the contaminationthat has adhered at the time of cutting.

Dust generation from the piezoelectric/electrostrictive device may causethe following problems. For example, in the case where thepiezoelectric/electrostrictive device is used in an actuator of amagnetic head in a hard disk drive, if dust is generated in the drive,the dust may cause crash of the floating slider onto the medium, therebyraising a fear of data destruction. Also, for thepiezoelectric/electrostrictive device itself, the dust may adhere to theelectrode of the piezoelectric/electrostrictive device, thereby givingrise to a fear of short circuit. For this reason, a high level ofcleaning is required not only in the hard disk drive but also in thedevice itself.

Therefore, an object of the present invention is to solve theaforementioned problems of the prior art by allowing the baseconstituting the piezoelectric/electrostrictive device of that form tohave an integral structure using one sheet of flat plate as an originalplate.

SUMMARY OF THE INVENTION

The present invention relates to a piezoelectric/electrostrictive deviceand a method of producing the piezoelectric/electrostrictive device. Thepiezoelectric/electrostrictive devices according to the presentinvention are piezoelectric/electrostrictive devices provided in thefollowing three types of forms.

A piezoelectric/electrostrictive device of the first form according tothe present invention is a piezoelectric/electrostrictive device thatincludes a base having a pair of right and left movable parts and afixing part that connects the movable parts with each other at one endthereof as well as a piezoelectric/electrostrictive element disposed onat least one side of the movable parts of the base.

A piezoelectric/electrostrictive device of the second form according tothe present invention is a piezoelectric/electrostrictive device thatincludes a base having a pair of right and left movable parts, a fixingpart that connects the movable parts with each other at one end thereof,and a mounting part that is separate from the fixing part and connectsthe movable parts with each other at the other end thereof as well as apiezoelectric/electrostrictive element disposed on at least one side ofthe movable parts of the base.

A piezoelectric/electrostrictive device of the third form according tothe present invention is a piezoelectric/electrostrictive device thatincludes a base having a pair of right and left movable parts, a fixingpart that connects the movable parts with each other at one end thereof,a mounting part that is separate from the fixing part and connects themovable parts with each other at the other end thereof, and a connectingpart that is integral with the mounting part and surrounds the mountingpart, the movable parts, and the fixing part as well as apiezoelectric/electrostrictive element disposed on at least one side ofthe movable parts of the base.

Now, in the piezoelectric/electrostrictive device of the first formaccording to the present invention, the base is constructed with onesheet of flat plate; the fixing part has a flat plate shape; and themovable parts are erect by a predetermined height from side peripheriesof the fixing part to face each other and extend beyond the other end ofthe fixing part along the side peripheries of the fixing part.

The piezoelectric/electrostrictive device can be constructed in such amanner that a slit-shaped groove extending from the other end of thefixing part intervenes between a base part of the movable partsconstituting the base and the side peripheries of the fixing part.Further, the piezoelectric/electrostrictive device can be constructed insuch a manner that a connecting portion between a base part of themovable parts and the side peripheries of the fixing part constitutingthe base has a circular arc shape.

In the piezoelectric/electrostrictive device of the second formaccording to the present invention, the base is constructed with onesheet of flat plate; the fixing part and the mounting part have a flatplate shape; and the movable parts are erect by a predetermined heightfrom side peripheries of the fixing part and the mounting part to faceeach other and extend along the side peripheries of the fixing part andthe mounting part.

The piezoelectric/electrostrictive device can be constructed in such amanner that a laterally extending slit-shaped groove intervenes betweenthe other end of the fixing part and the one end of the mounting partconstituting the base, and a longitudinally extending slit-shaped grooveintervenes between a base part of the movable parts and the sideperipheries of the fixing part and the mounting part. Alternatively, thepiezoelectric/electrostrictive device can be constructed in such amanner that a laterally and longitudinally extending rectangular openingintervenes between the other end of the fixing part and the one end ofthe mounting part constituting the base. Further, thepiezoelectric/electrostrictive device can be constructed in such amanner that a connecting portion between a base part of the movableparts and the side peripheries of the fixing part constituting the basehas a circular arc shape.

In the piezoelectric/electrostrictive device of the third form accordingto the present invention, the base is constructed with one sheet of flatplate; the fixing part and the mounting part have a flat plate shape;the movable parts are erect by a predetermined height from sideperipheries of the fixing part and the mounting part to face each otherand extend along the side peripheries of the fixing part and themounting part; and the movable parts, the fixing part, and the mountingpart are positioned within a central space of the connecting part.

The piezoelectric/electrostrictive device can be constructed in such amanner that the central space of the connecting part on a side of theone end of the fixing part is either closed or open. Further, thepiezoelectric/electrostrictive device can be constructed in such amanner that a connecting portion between a base part of the movableparts and the side peripheries of the fixing part constituting the basehas a circular arc shape. Still further, thepiezoelectric/electrostrictive device can be constructed in such amanner that a connecting portion between a base part of the movableparts and the side peripheries of the fixing part and the mounting partconstituting the base has a circular arc shape.

The piezoelectric/electrostrictive devices of these forms according tothe present invention can employ the following constructions, namely, aconstruction such that the base is constructed with a flat plate made ofmetal; a construction such that a central portion, as viewed in a lengthdirection, of the movable parts constituting the base is formed to havea smaller thickness than other portions of the movable parts; aconstruction such that the movable parts constituting the base has areinforcing part located at an end thereof on the fixing part side andbent from an upper edge of the end to extend towards and abut against asurface of the fixing part; a construction such that the movable partsconstituting the base has a reinforcing part located at an end thereofon the fixing part side and bent from a front edge of the end to extendtowards an inner side and abut against a surface of the fixing part; anda construction such that a reinforcing member intervenes between themovable parts on the fixing part constituting the base. Furthermore, thepiezoelectric/electrostrictive devices can employ a construction suchthat the fixing part constituting the base extends from the one end sideof the movable parts and is enlarged as compared with a case of beinglocated within the movable parts, and a construction such that themounting part constituting the base extends from the other end side ofthe movable parts and is enlarged as compared with a case of beinglocated within the movable parts.

The methods of producing a piezoelectric/electrostrictive deviceaccording to the present invention are directed to methods ofrespectively producing piezoelectric/electrostrictive devices of theabove-described three forms, and the methods of producing thepiezoelectric/electrostrictive devices of these various forms are asfollows.

The first production method according to the present invention is amethod of producing a piezoelectric/electrostrictive device of the firstform according to the present invention, wherein the method includes thesteps of preparing a flexible and bendable flat plate as a material forforming the base, stamping the flat plate into a shape that delineates aplane development of the base to form a stamped structure, and bendingthe stamped structure at a predetermined site to form the base havingthe movable parts and the fixing part.

The production method can be carried out in such a manner that thestamped structure has a gate-shaped opening composed of a pair ofstraight side grooves located at right and left sides of a rectangularflat plate and extending along side peripheries and an opening formed bycutting and removing a portion between the two grooves, and the sideperipheries of the flat plate are bent along the side grooves to formthe side peripheries into the movable parts and to form a portionbetween the side grooves into the fixing part.

The second production method according to the present invention is amethod of producing a piezoelectric/electrostrictive device of thesecond form according to the present invention, wherein the methodincludes the steps of preparing a flexible and bendable flat plate as amaterial for forming the base, stamping the flat plate into a shape thatdelineates a plane development of the base to form a stamped structure,and bending the stamped structure at a predetermined site to form thebase having the movable parts, the fixing part, and the mounting part.

The production method can be carried out in such a manner that thestamped structure has an H-shaped opening composed of a pair of straightside grooves located at right and left sides of a rectangular flat plateand extending along side peripheries and a straight central groove thatconnects the two side grooves with each other at a middle part, and theside peripheries of the flat plate are bent along the side grooves toform the side peripheries into the movable parts and to form a portionbetween the side grooves into the fixing part and the mounting part.Further, the production method can be carried out in such a manner thatthe stamped structure has a rectangular opening at a central part of arectangular flat plate, and side peripheries of the flat plate are bentalong side peripheries of the opening to form the side peripheries intothe movable parts and to form a portion between the side peripheriesinto the fixing part and the mounting part.

The third production method according to the present invention is amethod of producing a piezoelectric/electrostrictive device of the thirdform according to the present invention, wherein the method includes thesteps of preparing a flexible and bendable flat plate as a material forforming the base, stamping the flat plate into a shape that delineates aplane development of the base to form a stamped structure, and bendingthe stamped structure at a predetermined site to form the base havingthe movable parts, the fixing part, the mounting part, and theconnecting part.

The production method can be carried out in such a manner that thestamped structure has a rectangular flat plate part located inside acentral opening of a rectangular flat plate and has an H-shaped openingcomposed of a pair of straight side grooves located at right and leftsides of the flat plate part and extending along side peripheries and astraight central groove that connects the two side grooves with eachother at a middle part, and the side peripheries of the flat plate partare bent along the side grooves to form the side peripheries into themovable parts, to form a portion between the side grooves into thefixing part and the mounting part, and to form a portion around thecentral opening into the connecting part.

The production methods according to the present invention can be carriedout in such a manner that a flat plate made of metal is adopted as amaterial for forming the base, and an opening of the stamped structureis formed by stamping simultaneously with stamping the flat plate orformed by a hole-forming process after stamping the flat plate.

Now, it is essential in the principle of operation that the fixing partor the fixing part and the mounting part are closely connected to thetwo flexible side peripheries. Since these are integrally formed in thepiezoelectric/electrostrictive devices according to the presentinvention, the most preferable modes are embodied in view of theprinciple of operation.

For example, in the case where the aforesaid two or three essentialparts are made of metal and welded with each other, one must take intoconsideration the problems in the heat treatment step, such asdistortion by heat of welding, deterioration of material quality, andannealing. In contrast, in the case where the base is integrally formedas in the piezoelectric/electrostrictive devices according to thepresent invention, these fears are absent even if the base is made ofmetal, and also an improvement in the strength of the connecting part byprocess hardening at the time of integral forming can be expected.

If the piezoelectric/electrostrictive device according to the presentinvention is combined with a component (for example, a magnetic head ofa hard disk drive), the height after assemblage will not be equal to thesum of the height of the component and the height of the device but willbe smaller than the sum, thereby producing an advantage that the devicecan have a compact construction. Regarding the height of the device, thethickness of the plate of the movable parts and the thickness of theadhesive are added to the height of the component; however, as comparedwith the known devices described at the beginning, the height afterassemblage can be reduced, thereby providing an effect of spacereduction. Further, the assemblage can be carried out with ease simplyby bonding the component onto the fixing part, and the bonding area canbe enlarged, thereby advantageously increasing the bonding strength andproviding a structure that will not be easily dropped off by impact.

In the first and second piezoelectric/electrostrictive devices among thepiezoelectric/electrostrictive devices according to the presentinvention, it is easy in view of their structure to form, by pressing, arecess to accommodate an adhesive at the bonding site of the mountingpart and the fixing part to the component to be controlled. This canincrease the bonding strength and can restrain the squeeze-out of theadhesive. Also, it is easy to form a standard position (hole or thelike) for positioning that is used in assembling the component. For thisreason, the assembling precision in assembling the component onto themounting part on the device and in mounting the fixing part onto thegimbal of the suspension in later steps can be increased to furtherimprove the yield of the products. By testing thepiezoelectric/electrostrictive element in advance before assembling thedevice, the deterioration of device characteristics after assembling thedevice can be greatly reduced.

It goes without saying that the piezoelectric/electrostrictive device ofthe third form according to the present invention can produce thefunctions and effects that are produced by the first and secondpiezoelectric/electrostrictive devices. In particular, since the thirdpiezoelectric/electrostrictive device has a connecting part that isintegral with the mounting part, the device provides a great advantagethat the connecting part can be allowed to function as a gimbal forsupporting the magnetic head (slider) of the hard disk drive.

The piezoelectric/electrostrictive devices according to the presentinvention are based on the piezoelectric/electrostrictive devices of theabove-described three forms. In these piezoelectric/electrostrictivedevices having a basic structure, the base of each device has anintegral structure formed from an original plate made of a flat plate,so that the base is in principle constructed with only one constructioncomponent. Therefore, the construction components of each device are twokinds, namely, the base and the piezoelectric/electrostrictive elements,so that the number of construction components of thepiezoelectric/electrostrictive device can be greatly reduced, and thenumber of steps for assembling the construction components can begreatly reduced, thereby leading to large reduction of costs.

Further, in each piezoelectric/electrostrictive device according to thepresent invention, since the number of construction components isextremely small and the number of bonding sites between the constructioncomponents is extremely small, there is little or no variation in theadhesion between the construction components, whereby thepiezoelectric/electrostrictive device has device characteristics inwhich the set precision is high.

Further, in forming each piezoelectric/electrostrictive device accordingto the present invention, there is no need to adopt means for cutting adevice master at numerous sites, so that there is no contaminationcaused by dusts and other contaminants generated at the time of cuttingthe device master. For this reason, if the base and thepiezoelectric/electrostrictive elements are cleaned in advance inassembling the piezoelectric/electrostrictive device, the assembledpiezoelectric/electrostrictive device has little or no contamination,thereby providing a great advantage that the step of cleaning thepiezoelectric/electrostrictive device can be omitted or carried out in asimple manner.

Regarding the piezoelectric/electrostrictive devices according to thepresent invention, the piezoelectric/electrostrictive device of thefirst form, the piezoelectric/electrostrictive device of the secondform, and the piezoelectric/electrostrictive device of the third formcan be produced with ease and at a low cost respectively by the firstmethod according to the present invention, the second method accordingto the present invention, and the third method according to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1K are perspective views respectively illustrating eleventypes of embodiments of the piezoelectric/electrostrictive devicesaccording to the present invention;

FIG. 2 is a perspective view illustrating a state in which a componentto be controlled is mounted on the first piezoelectric/electrostrictivedevice of the second form according to the present invention;

FIGS. 3A and 3B are a perspective view illustrating an original plate ofa base constituting the first piezoelectric/electrostrictive device, anda perspective view illustrating the base formed by bending the originalplate, respectively;

FIGS. 4A and 4B are a perspective view illustrating a state ofassembling the first piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 5A and 5B are a perspective view illustrating an original plate ofa base constituting the second piezoelectric/electrostrictive device ofthe second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 6A and 6B are a perspective view illustrating a state ofassembling the second piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 7A and 7B are a perspective view illustrating an original plate ofa base constituting the third piezoelectric/electrostrictive device ofthe second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 8A and 8B are a perspective view illustrating a state ofassembling the third piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 9A and 9B are a perspective view illustrating an original plate ofa base constituting the fourth piezoelectric/electrostrictive device ofthe second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 10A and 10B are a perspective view illustrating a state ofassembling the fourth piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 11A and 11B are a perspective view illustrating an original plateof a base constituting the fifth piezoelectric/electrostrictive deviceof the second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 12A and 12B are a perspective view illustrating a state ofassembling the fifth piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 13A and 13B are a perspective view illustrating an original plateof a base constituting the sixth piezoelectric/electrostrictive deviceof the second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 14A and 14B are a perspective view illustrating a state ofassembling the sixth piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 15A and 15B are a perspective view illustrating an original plateof a base constituting the seventh piezoelectric/electrostrictive deviceof the seventh embodiment according to the present invention, and aperspective view illustrating the base formed by bending the originalplate, respectively;

FIGS. 16A and 16B are a perspective view illustrating a state ofassembling the seventh piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 17A and 17B are a perspective view illustrating an original plateof a base constituting the eighth piezoelectric/electrostrictive deviceof the first form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 18A and 18B are a perspective view illustrating a state ofassembling the eighth piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIG. 19 is a perspective view illustrating a state in which a componentto be controlled is mounted on the first modification of the eighthpiezoelectric/electrostrictive device;

FIG. 20 is a perspective view illustrating the second modification ofthe eighth piezoelectric/electrostrictive device;

FIGS. 21A and 21B are a perspective view illustrating an original plateof a base constituting the ninth piezoelectric/electrostrictive deviceof the second form according to the present invention, and a perspectiveview illustrating the base formed by bending the original plate,respectively;

FIGS. 22A and 22B are a perspective view illustrating a state ofassembling the ninth piezoelectric/electrostrictive device, and aperspective view illustrating the assembledpiezoelectric/electrostrictive device, respectively;

FIGS. 23A and FIG. 23B are perspective views illustrating two examplesof piezoelectric/electrostrictive elements adopted as thepiezoelectric/electrostrictive element constituting thepiezoelectric/electrostrictive device according to the presentinvention;

FIGS. 24A and FIG. 24B are perspective views illustrating two otherexamples of piezoelectric/electrostrictive elements adopted as thepiezoelectric/electrostrictive element constituting thepiezoelectric/electrostrictive device according to the presentinvention;

FIG. 25 is a perspective view illustrating the firstpiezoelectric/electrostrictive device in which thepiezoelectric/electrostrictive element shown in FIG. 24B is adopted asthe piezoelectric/electrostrictive element;

FIG. 26 is a plan view illustrating a non-operating state of thepiezoelectric/electrostrictive device of FIG. 25;

FIGS. 27A and 27B are waveform diagrams respectively showing voltagesapplied to the two piezoelectric/electrostrictive elements of thepiezoelectric/electrostrictive device of FIG. 25;

FIG. 28 is a plan view illustrating an operating state of thepiezoelectric/electrostrictive device of FIG. 25;

FIG. 29 is a perspective view illustrating the first modification of thefirst piezoelectric/electrostrictive device;

FIG. 30 is a perspective view illustrating the second modification ofthe first piezoelectric/electrostrictive device;

FIG. 31 is a perspective view illustrating the tenthpiezoelectric/electrostrictive device of the third form according to thepresent invention;

FIGS. 32A and 32B are a perspective view illustrating an original plateof a base constituting the piezoelectric/electrostrictive device of FIG.31, and a perspective view illustrating the base formed by bending theoriginal plate, respectively;

FIG. 33 is a perspective view illustrating the eleventhpiezoelectric/electrostrictive device of the third form according to thepresent invention;

FIGS. 34A and 34B are a perspective view illustrating an original plateof a base constituting the piezoelectric/electrostrictive device of FIG.33, and a perspective view illustrating the base formed by bending theoriginal plate, respectively;

FIG. 35 is a perspective view illustrating a hard disk drive having thetenth piezoelectric/electrostrictive device mounted thereon; and

FIGS. 36A and 36B are a plan view and a side view, respectively, of asuspension having the tenth piezoelectric/electrostrictive devicemounted thereon.

FIG. 37 is a perspective view illustrating a twelfthpiezoelectric/electrostrictive device.

FIG. 38A is a perspective view illustrating a state before apiezoelectric/electrostrictive element is bonded to an original plate ofa base constituting the twelfth piezoelectric/electrostrictive device.

FIG. 38B is a perspective view illustrating a state after thepiezoelectric/electrostrictive element is bonded to the original plateof the base constituting the twelfth piezoelectric/electrostrictivedevice.

FIG. 39 is a perspective view illustrating a thirteenthpiezoelectric/electrostrictive device.

FIG. 40A is a perspective view illustrating a state before thepiezoelectric/electrostrictive element is bonded to an original plate ofa base constituting the thirteenth piezoelectric/electrostrictivedevice.

FIG. 40B is a perspective view illustrating a state after thepiezoelectric/electrostrictive element is bonded to the original plateof the base constituting the thirteenth piezoelectric/electrostrictivedevice.

FIG. 41A is a perspective view illustrating a state before the originalplate of the base constituting the thirteenthpiezoelectric/electrostrictive device after having bonded thepiezoelectric/electrostrictive element thereon is bent.

FIG. 41B is a perspective view illustrating a state after the originalplate of the base constituting the thirteenthpiezoelectric/electrostrictive device after having bonded thepiezoelectric/electrostrictive element thereon is bent.

FIG. 42 is a perspective view of a fourteenthpiezoelectric/electrostrictive device.

FIG. 43A is a perspective view illustrating a state before an originalplate of a base constituting the fourteenthpiezoelectric/electrostrictive device is bent.

FIG. 43B is a perspective view illustrating a state after the originalplate of the base constituting the fourteenthpiezoelectric/electrostrictive device is bent.

FIG. 44 is a perspective view illustrating a first modification of thefourteenth piezoelectric/electrostrictive device.

FIG. 45 is a perspective view illustrating a second modification of thefourteenth piezoelectric/electrostrictive device.

FIG. 46 is a perspective view illustrating a third modification of thefourteenth piezoelectric/electrostrictive device.

FIG. 47 is a perspective view illustrating a fourth modification of thefourteenth piezoelectric/electrostrictive device.

FIG. 48 is a perspective view illustrating a state before a reinforcingmember having a piezoelectric/electrostrictive element which constitutesa fifteenth piezoelectric/electrostrictive device bonded thereon isbonded on a base.

FIG. 49 is a perspective view showing a state after the reinforcingmember having the piezoelectric/electrostrictive element whichconstitutes the fifteenth piezoelectric/electrostrictive device bondedthereon is bonded on the base.

FIG. 50 is a perspective view illustrating the fifteenthpiezoelectric/electrostrictive device.

FIG. 51 is a perspective view showing a state before a reinforcingmember having a piezoelectric/electrostrictive element which constitutesa first modification of the fifteenth piezoelectric/electrostrictivedevice bonded thereon is bonded on the base.

FIG. 52 is a perspective view illustrating the first modification of thefifteenth piezoelectric/electrostrictive device.

FIG. 53 is a perspective view illustrating a state before thereinforcing member having a piezoelectric/electrostrictive element whichconstitutes a second modification of the fifteenthpiezoelectric/electrostrictive device bonded thereon is bonded on thebase.

FIG. 54 is a perspective view illustrating the second modification ofthe fifteenth piezoelectric/electrostrictive device.

FIG. 55 is a perspective view illustrating a third modification of thefifteenth piezoelectric/electrostrictive device.

FIG. 56 is a perspective view illustrating a fourth modification of thefifteenth piezoelectric/electrostrictive device.

FIG. 57 is a perspective view illustrating a fifth modification of thefifteenth piezoelectric/electrostrictive device.

FIG. 58 is a perspective view illustrating an example in which thereinforcing member is inserted into movable parts of the firstpiezoelectric/electrostrictive device shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The piezoelectric/electrostrictive devices according to the presentinvention are: a piezoelectric/electrostrictive device of the first formthat includes a base having a pair of right and left movable parts and afixing part that connects the movable parts with each other at one endthereof as well as a piezoelectric/electrostrictive element disposed onat least one side of the movable parts of the base; apiezoelectric/electrostrictive device of the second form that includes abase having a pair of right and left movable parts, a fixing part thatconnects the movable parts with each other at one end thereof, and amounting part that is separate from the fixing part and connects themovable parts with each other at the other end thereof as well as apiezoelectric/electrostrictive element disposed on at least one side ofthe movable parts of the base; and a piezoelectric/electrostrictivedevice of the third form that includes a base having a pair of right andleft movable parts, a fixing part that connects the movable parts witheach other at one end thereof, a mounting part that is separate from thefixing part and connects the movable parts with each other at the otherend thereof, and a connecting part that is integral with the mountingpart and surrounds the mounting part, the movable parts, and the fixingpart as well as a piezoelectric/electrostrictive element disposed on atleast one side of the movable parts of the base. FIGS. 1A to 1Killustrate numerous embodiments (first embodiment to eleventhembodiment) of the piezoelectric/electrostrictive devices of variousforms.

The first piezoelectric/electrostrictive device 10 a shown in FIG. 1Abelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention and is used in astate shown in FIG. 2. The first piezoelectric/electrostrictive device10 a is formed by the method shown in FIGS. 3 and 4. The firstpiezoelectric/electrostrictive device 10 a is made of a base 11 and apair of piezoelectric/electrostrictive elements 12 a, 12 b. Base 11 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 11 a, 11 b, a flat plate-shaped fixing part 11 c thatconnects the movable parts 11 a, 11 b with each other at one endthereof, and a flat plate-shaped mounting part 11 d that connects themovable parts 11 a, 11 b with each other at the other end thereof.

An H-shaped opening 11 e sections base 11 into movable parts 11 a, 11 b,fixing part 11 c, and mounting part 11 d. Opening 11 e is made of a pairof right and left side grooves 11 e 1, 11 e 2 and a central groove 11 e3 that connects the two side grooves 11 e 1, 11 e 2 with each other atthe central part thereof as viewed in the longitudinal direction.Movable part 11 a on the left side is bent at side groove 11 e 1 alonggroove 11 e 1 and is erect perpendicularly to fixing part 11 c andmounting part 11 d. Similarly, movable part 11 b on the right side isbent at side groove 11 e 2 along groove 11 e 2 and is erectperpendicularly to fixing part 11 c and mounting part 11 d.

In base 11 having such a construction, piezoelectric/electrostrictiveelements 12 a, 12 b are bonded respectively onto outer sides of themovable parts 11 a, 11 b via an adhesive made of epoxy resin or thelike. Piezoelectric/electrostrictive elements 12 a, 12 b are each amulti-layer body made of piezoelectric/electrostrictive layers andelectrode films. Piezoelectric/electrostrictive elements 12 a, 12 b areformed to have the same shape as movable parts 11 a, 11 b and areshorter than movable parts 11 a, 11 b by a predetermined length.Piezoelectric/electrostrictive elements 12 a, 12 b are respectivelybonded in alignment to the end of movable parts 11 a, 11 b on the fixingpart 11 c side, and extend to a site that leaves a predetermined lengthfrom the end of movable parts 11 a, 11 b on the mounting part 11 d side.

In the base 11, a magnetic head H (slider) for a hard disk, which is acomponent to be controlled, for example, is bonded and fixed onto theupper side of mounting part 11 d, and the lower side is bonded and fixedonto a gimbal of the suspension. Here, in this case, the positions ofmounting the magnetic head H and the suspension can be changed to fixingpart 11 c, contrary to the above. This does not change the devicefunctions at all. Also, the positions of mounting the magnetic head Hand the suspension with respect to fixing part 11 c and mounting part 11d can be changed to a configuration in which the roles of the front andrear surfaces are reversed. This does not change the device functions atall, either. However, the wirings of external electrodes that arebrought into contact with the terminals ofpiezoelectric/electrostrictive elements 12 a, 12 b must be wired in areversed manner on the suspension.

Now, base 11 constituting the piezoelectric/electrostrictive device 10 ais formed by using an original plate 11A shown in FIG. 3A as a materialfor molding and by bending original plate 11A as shown in FIG. 3B.Original plate 11A is a stamped structure that is stamped out from aflexible and bendable flat plate and is formed in a shape thatdelineates a plane development of base 11. The flat plate constitutingthe original plate 11A is preferably made of metal in view of strength.

The flat plate is preferably made of a metal having a Young's modulus ofat least 100 GPa and, as a ferrous metals material, one can mentionaustenite-series stainless steels such as SUS301, SUS304, AISI653, andSUH660, ferrite-series stainless steels such as SUS430 and SUS434,martensite-series stainless steels such as SUS410 and SUS630,semiaustenite-series stainless steels such as SUS6312 and AISI632,maraging stainless steel, various spring steel materials, and others. Asa nonferrous metals material, one can mention super elastic titaniumalloys such as a titanium-nickel alloy, brass, nickel, aluminum,tungsten, molybdenum, beryllium copper, phosphorus bronze, nickel, anickel iron alloy, titanium, and others.

Original plate 11A is formed by subjecting a flat plate to a stampingprocess, and is provided with an H-shaped opening 11 e. Opening 11 e isformed simultaneously at the time of stamping the flat plate, and ismade of a pair of straight side grooves 11 e 1, 11 e 2 located at rightand left sides of original plate 11A and extending to the front and rearends and a straight central groove 11 e 3 that connects the two sidegrooves 11 e 1, 11 e 2 with each other at the central parts thereof.Base 11 is formed by perpendicularly bending the right and left sideperipheries of original plate 11A at the side grooves 11 e 1, 11 e 2along central lines L1, L2 that extend at the center of the width of thegrooves 11 e 1, 11 e 2 in the longitudinal direction thereof. By bendingthe right and left sides of original plate 11A in such a manner, thesites located outside the side grooves 11 e 1, 11 e 2 are formed intomovable parts 11 a, 11 b, and the sites on the front end side and on therear end side of the central groove 11 e 3 are formed into fixing part11 c and mounting part 11 d, respectively.

In base 11 thus integrally constructed from original plate 11A,piezoelectric/electrostrictive elements 12 a, 12 b are bonded via anadhesive onto the outer sides of movable parts 11 a, 11 b as shown inFIG. 4A to form piezoelectric/electrostrictive device 10 a shown in FIG.4B. Piezoelectric/electrostrictive device 10 a thus formed functions inthe same manner as the conventional piezoelectric/electrostrictivedevices of this form and, since base 11 is integrally constructed fromoriginal plate 11A, piezoelectric/electrostrictive device 10 a producesthe following functions and effects.

Namely, in the first piezoelectric/electrostrictive device 10 a, base 11has an integral structure made of one sheet of original plate 11A aloneand is constructed with one construction component. Therefore, theconstruction components of the device 10 a are two kinds, i.e. base 11and piezoelectric/electrostrictive elements 12 a, 12 b, so that thenumber of construction components of piezoelectric/electrostrictivedevice 10 a can be greatly reduced, and the number of steps forassembling the construction components can be greatly reduced, therebyleading to large reduction of costs.

Further, in the first piezoelectric/electrostrictive device 10 a, sincethe number of construction components is extremely small and the numberof bonding sites between the construction components is extremely small,there is little or no variation in the adhesion between the constructioncomponents, whereby the first piezoelectric/electrostrictive device 10 ahas device characteristics in which the set precision is high.

Further, in forming the first piezoelectric/electrostrictive device 10a, there is no need to adopt means for cutting a device master atnumerous sites as in the prior art, so that there is no contaminationcaused by adhesion of dusts and other contaminants generated at the timeof cutting the device master. For this reason, if base 11 andpiezoelectric/electrostrictive elements 12 a, 12 b are cleaned inadvance in assembling the first piezoelectric/electrostrictive device 10a, the assembled piezoelectric/electrostrictive device 10 a has littleor no contamination, thereby providing a great advantage that the stepof cleaning the piezoelectric/electrostrictive devβÿβ 10 a can beomitted or carried out in a simple manner.

The second piezoelectric/electrostrictive device 10 b shown in FIG. 1Bbelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The secondpiezoelectric/electrostrictive device 10 b has a base constructed in aslightly different manner from that of the firstpiezoelectric/electrostrictive device 10 a. Referring to FIG. 6B, thesecond piezoelectric/electrostrictive device 10 b is made of a base 13and a pair of piezoelectric/electrostrictive elements 12 a, 12 b. Base13 is constructed with a pair of right and left long and narrowplate-shaped movable parts 13 a, 13 b, a flat plate-shaped fixing part13 c that connects the movable parts 13 a, 13 b with each other at oneend thereof, and a flat plate-shaped mounting part 13 d that connectsthe movable parts 13 a, 13 b with each other at the other end thereof.

An H-shaped opening 13 e sections base 13 into movable parts 13 a, 13 b,fixing part 13 c, and mounting part 13 d. As far as such a constructionis concerned, the base 13 of the second piezoelectric/electrostrictivedevice 10 b has the same construction as the base 11 of the firstpiezoelectric/electrostrictive device 10 a.

However, in base 13, the bent parts 13 a 1, 13 b 1, which are the sitesfor connecting movable parts 13 a, 13 b to fixing part 13 c and mountingpart 13 d, have a circular arc shape in which the bent parts 13 a 1, 13b 1 are recessed from the surface of fixing part 13 c and mounting part13 d. Referring to FIG. 5A, the original plate 13A constituting the base13 is the same as the original plate 11A of base 11, and has a differentbent shape in bending the original plate to form movable parts 13 a, 13b. Namely, in the bending process, circular arc-shaped bent parts 13 a1, 13 b 1 are formed at the base part of movable parts 13 a, 13 b.Referring to FIG. 6A, piezoelectric/electrostrictive elements 12 a, 12 bare bonded onto the outer sides of movable parts 13 a, 13 b of the base13 to form the second piezoelectric/electrostrictive device 10 b.

The second piezoelectric/electrostrictive device 10 b has the samefunctions as the first piezoelectric/electrostrictive device 10 a andproduces approximately similar actions and effects as the firstpiezoelectric/electrostrictive device 10 a. In particular, since movableparts 13 a, 13 b are connected to fixing part 13 c and mounting part 13d via circular arc-shaped bent parts 13 a 1, 13 b 1, the movability ofmovable parts 13 c, 13 d is improved to produce high device functions.

Further, the second piezoelectric/electrostrictive device 10 bfacilitates making a highly precise degree of orthogonality of movableparts 13 a, 13 b to fixing part 13 c and mounting part 13 d, therebyrestraining displacements in the flapping direction. Moreover, since theposition of movable parts 13 a, 13 b in the Y-axis direction withrespect to fixing part 13 c and mounting part 13 d can be set bychanging the degree of bending the circular arc-shaped bent parts, thedevice designing can have a larger width.

The third piezoelectric/electrostrictive device 10 c shown in FIG. 1Cbelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The thirdpiezoelectric/electrostrictive device 10 c has a base constructed tohave slightly different parts from those of the secondpiezoelectric/electrostrictive device 10 b, but the other parts are thesame.

Now, referring to FIG. 8B, the third piezoelectric/electrostrictivedevice 10 c is made of a base 14 and a pair ofpiezoelectric/electrostrictive elements 12 a, 12 b. Base 14 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 14 a, 14 b, a flat plate-shaped fixing part 14 c thatconnects the movable parts 14 a, 14 b with each other at one endthereof, and a flat plate-shaped mounting part 14 d that connects themovable parts 14 a, 14 b with each other at the other end thereof.

In base 14, the middle portion of movable parts 14 a, 14 b in thelongitudinal is formed into thin parts 14 a 1, 14 b 1 for apredetermined length; however, except this point, base 14 is constructedin the same manner as base 13. Further, referring to FIG. 7A, theoriginal plate 14A of base 14 has thin parts 14 a 1, 14 b 1 on the rightand left sides of an H-shaped opening 14 e which are to be formed intomovable parts 14 a, 14 b later. Base 14 is subjected to a bendingprocess along the two-dot chain lines L1, L2 shown in FIG. 7B in thesame manner as base 13. Referring to FIG. 8A,piezoelectric/electrostrictive elements 12 a, 12 b are bonded onto outersides of movable parts 14 a, 14 b to form the thirdpiezoelectric/electrostrictive device 10 c.

The third piezoelectric/electrostrictive device 10 c has the samefunctions as the second piezoelectric/electrostrictive device 10 b andproduces approximately similar actions and effects as the secondpiezoelectric/electrostrictive device 10 b. In particular, since movableparts 14 a, 14 b are provided with thin parts 14 a 1, 14 b 1 that arelocated in the middle thereof and extending in the longitudinaldirection, the movability of movable parts 14 a, 14 b is more enhancedto produce further high device functions.

Here, as means for forming thin parts 14 a 1, 14 b 1 of original plate14A, one can adopt a method of reducing the thickness by partiallyremoving the material using chemical etching, microblasting,ion-milling, or the like, or a method of reducing the thickness bycutting through grinding, or the like method. Further, as a specialmeans, one can adopt a plate formed by superposing and bonding one platethat has been drilled to have a hole of a predetermined length onto theother plate without a hole to substitute the site corresponding to thehole for the thin parts, as an original plate.

The fourth piezoelectric/electrostrictive device 10 d shown in FIG. 1Dbelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The fourthpiezoelectric/electrostrictive device 10 d has a base constructed tohave slightly different parts from those of the firstpiezoelectric/electrostrictive device 10 a, but the other parts are thesame.

Referring to FIG. 10B, the fourth piezoelectric/electrostrictive device10 d is made of a base 15 and a pair of piezoelectric/electrostrictiveelements 12 a, 12 b. Base 15 is constructed with a pair of right andleft long and narrow plate-shaped movable parts 15 a, 15 b, a flatplate-shaped fixing part 15 c that connects the movable parts 15 a, 15 bwith each other at one end thereof, a flat plate-shaped mounting part 15d that connects the movable parts 15 a, 15 b with each other at theother end thereof, and a pair of right and left reinforcing parts 15 f,15 g that extend from an upper fringe on one ends of movable parts 15 a,15 b and abut against the surface of fixing part 15 c.

Base 15 is constructed in the same manner as base 11 except that base 15is provided with reinforcing parts 15 f, 15 g. Further, referring toFIG. 9A, the original plate 15A of base 15 is provided with portions tobecome reinforcing parts 15 f, 15 g that are extending outward from oneends of the right and left sides of an H-shaped opening 15 e which areto be formed into movable parts 15 a, 15 b later. Base 15 is subjectedto a bending process along two-dot chain lines L1, L2 and others asshown in FIG. 9B. Referring to FIG. 10A, piezoelectric/electrostrictiveelements 12 a, 12 b are bonded onto outer sides of movable parts 15 a,15 b to form the fourth piezoelectric/electrostrictive device 10 d.

The fourth piezoelectric/electrostrictive device 10 d has the samefunctions as the first piezoelectric/electrostrictive device 10 a andproduces approximately similar actions and effects as the firstpiezoelectric/electrostrictive device 10 a. In particular, fixing part15 c is reinforced by reinforcing parts 15 f, 15 g. Reinforcing parts 15f, 15 g are bonded onto fixing part 15 c. As the bonding means therefor,one can adopt a bonding means such as spot welding, press-bonding,caulking, soldering, brazing, or using an adhesive such as epoxy resinor UV-curing type resin or the like. Among these bonding means, spotwelding is especially preferable.

The fifth piezoelectric/electrostrictive device 10 e shown in FIG. 1Ebelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The fifthpiezoelectric/electrostrictive device 10 e has a base constructed tohave slightly different parts from those of the fourthpiezoelectric/electrostrictive device 10 d, but the other parts are thesame.

Now, referring to FIG. 12B, the fifth piezoelectric/electrostrictivedevice 10 e is made of a base 16 and a pair ofpiezoelectric/electrostrictive elements 12 a, 12 b. Base 16 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 16 a, 16 b, a flat plate-shaped fixing part 16 c thatconnects the movable parts 16 a, 16 b with each other at one endthereof, a flat plate-shaped mounting part 16 d that connects themovable parts 16 a, 16 b with each other at the other end thereof, andreinforcing parts 16 f, 16 g that bend inwardly from the end of movableparts 16 a, 16 b in a manner like a flange.

Base 16 is constructed in the same manner as base 15 except that theshape of reinforcing parts 16 f, 16 g is different from the shape ofreinforcing parts 15 f, 15 g. Further, referring to FIG. 11A, theoriginal plate 16A of base 16 is constructed in such a manner that theright and left sides of an H-shaped opening 16 e, which are to be formedinto movable parts 16 a, 16 b later, protrude both forwardly andrearwardly for a predetermined length. Referring to FIG. 11B, base 16 issubjected to a bending process along two-dot chain lines L1, L2 andothers shown in FIG. 11A. Referring to FIG. 12A,piezoelectric/electrostrictive elements 12 a, 12 b are bonded onto outersides of movable parts 16 a, 16 b to form the fifthpiezoelectric/electrostrictive device 10 e.

Here, in the fifth piezoelectric/electrostrictive device 10 e,reinforcing parts 16 f, 16 g are bonded to neither fixing part 16 c normounting part 16 d; however, reinforcing parts 16 f, 16 g are morepreferably bonded to fixing part 16 c and mounting part 16 d. As thebonding means therefor, one can adopt a bonding means such as spotwelding, press-bonding, caulking, soldering, brazing, or using anadhesive such as epoxy resin or UV-curing type resin or the like. Amongthese bonding means, spot welding is especially preferable.

The fifth piezoelectric/electrostrictive device 10 e has the samefunctions as the first piezoelectric/electrostrictive device 10 a andproduces approximately similar actions and effects as the firstpiezoelectric/electrostrictive device 10 a. In particular, fixing part16 c and mounting part 16 d are reinforced by reinforcing parts 16 f, 16g.

The sixth piezoelectric/electrostrictive device 10 f shown in FIG. 1Fbelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The sixthpiezoelectric/electrostrictive device 10 f is different from the firstpiezoelectric/electrostrictive device 10 a in that a reinforcing memberis added to the base, but the other parts are the same.

Now, referring to FIG. 14B, the sixth piezoelectric/electrostrictivedevice 10 f is made of a base 17 and a pair ofpiezoelectric/electrostrictive elements 12 a, 12 b. Base 17 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 17 a, 17 b, a flat plate-shaped fixing part 17 c thatconnects the movable parts 17 a, 17 b with each other at one endthereof, a flat plate-shaped mounting part 17 d that connects themovable parts 17 a, 17 b with each other at the other end thereof, and aplate-shaped reinforcing member 17 f inserted between the sides at oneends of movable parts 17 a, 17 b and bonded to the surface of fixingpart 17 c.

Referring to FIG. 13A, the original plate 17A of base 17 has the sameshape as the original plate 11A of base 11. Referring to FIG. 13B, base17 is subjected to a bending process along two-dot chain lines L1, L2.Referring to FIG. 14A, reinforcing member 17 f is bonded onto thesurface of fixing part 17 c between the sides at one end of movableparts 17 a, 17 b, and piezoelectric/electrostrictive elements 12 a, 12 bare bonded onto outer sides of movable parts 17 a, 17 b to form thesixth piezoelectric/electrostrictive device 10 f. The sixthpiezoelectric/electrostrictive device 10 f has the same functions as thefourth piezoelectric/electrostrictive device 10 d and producesapproximately similar actions and effects as the fourthpiezoelectric/electrostrictive device 10 d.

The seventh piezoelectric/electrostrictive device log shown in FIG. 1Gbelongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The seventhpiezoelectric/electrostrictive device 10 g is different from the firstpiezoelectric/electrostrictive device 10 a in that the fixing part andthe mounting part of the base are differently shaped, but the otherparts are the same.

Now, referring to FIG. 16B, the seventh piezoelectric/electrostrictivedevice 10 g is made of a base 18 and a pair ofpiezoelectric/electrostrictive elements 12 a, 12 b. Base 18 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 18 a, 18 b, a flat plate-shaped fixing part 18 c thatconnects the movable parts 18 a, 18 b with each other at one endthereof, and a flat plate-shaped mounting part 18 d that connects themovable parts 18 a, 18 b with each other at the other end thereof.Fixing part 18 c protrudes for a predetermined length from one ends ofmovable parts 18 a, 18 b, and mounting part 18 d protrudes for apredetermined length from the other ends of movable parts 18 a, 18 b.Therefore, fixing part 18 c and mounting part 18 d are an enlargement offixing part 11 c and mounting part 11 d in base 11 of the firstpiezoelectric/electrostrictive device 10 a, thereby ensuring a largerarea.

Base 18 is constructed in the same manner as base 11 except that theareas of fixing part 18 c and mounting part 18 d are enlarged. Further,referring to FIG. 15A, the original plate 18A of base 18 is constructedin such a manner that the front and rear sides of an H-shaped opening 18e, which are to be formed into fixing part 18 c and mounting part 18 dlater, protrude forwardly and rearwardly for a predetermined length.Referring to FIG. 15B, base 18 is subjected to a bending process alongtwo-dot chain lines L1, L2. Referring to FIG. 16A,piezoelectric/electrostrictive elements 12 a, 12 b are bonded onto outersides of movable parts 18 a, 18 b to form the seventhpiezoelectric/electrostrictive device 10 g.

The seventh piezoelectric/electrostrictive device 10 g has the samefunctions as the first piezoelectric/electrostrictive device 10 a andproduces approximately similar actions and effects as the firstpiezoelectric/electrostrictive device 10 a. In particular, since fixingpart 18 c and mounting part 18 d each have a larger area, the bondingarea to the gimbal of the suspension can be enlarged, and the bondingarea to the component to be controlled, such as the magnetic head of thehard disk drive, can be enlarged.

The eighth piezoelectric/electrostrictive device 20 a shown in FIG. 1Hbelongs to the category of the piezoelectric/electrostrictive device ofthe first form according to the present invention. The eighthpiezoelectric/electrostrictive device 20 a has a base constructed in agreatly different manner from that of the firstpiezoelectric/electrostrictive device 10 a.

Now, referring to FIG. 18B, the eighth piezoelectric/electrostrictivedevice 20 a is made of a base 21 and a pair ofpiezoelectric/electrostrictive elements 22 a, 22 b. Base 21 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 21 a, 21 b and a flat plate-shaped fixing part 21 c thatconnects the movable parts 21 a, 21 b with each other at one endthereof. However, a mounting part is not provided on the other ends ofmovable parts 21 a, 21 b.

Referring to FIG. 17A, the original plate 21A of base 21 is formed bysubjecting a flat plate to a stamping process, and is provided with agate-shaped opening 21 d. Opening 21 d has a shape provided with a pairof straight side grooves 21 d 1, 21 d 2 located at right and left sidesof the flat plate and extending to the front and rear ends, and an opensite 21 d 3 obtained by cutting and removing the other end locatedbetween these two grooves 21 d 1, 21 d 2. Base 21 is formed byperpendicularly bending the right and left sides of original plate 21Aat the side grooves 21 d 1, 21 d 2 along central lines L1, L2 thatextend at the center of the width of the grooves 21 d 1, 21 d 2 in thelongitudinal direction thereof, as shown in FIG. 17B. By bending theright and left sides of original plate 21A in such a manner, the siteslocated outside the side grooves 21 d 1, 21 d 2 are formed into movableparts 21 a, 21 b, and the site between the side grooves 21 d 1, 21 d 2is formed into fixing part 21 c.

In base 21 thus integrally constructed from original plate 21A,piezoelectric/electrostrictive elements 22 a, 22 b are bonded via anadhesive onto the outer sides of movable parts 21 a, 21 b as shown inFIG. 18A to form piezoelectric/electrostrictive device 20 a shown inFIG. 18B. Piezoelectric/electrostrictive device 20 a thus formedfunctions in the same manner as the conventionalpiezoelectric/electrostrictive devices of this form by being used in astate in which a component to be controlled, such as a magnetic head, isbonded between the other ends of movable parts 21 a, 21 b. However,since base 21 is integrally constructed from one sheet of original plate21A, piezoelectric/electrostrictive device 20 a produces the followingfunctions and effects.

Namely, in the eighth piezoelectric/electrostrictive device 20 a, base21 has an integral structure made of original plate 21A and isconstructed with one construction component. Therefore, the constructioncomponents are two kinds, i.e. base 21 andpiezoelectric/electrostrictive elements 22 a, 22 b, so that the numberof construction components of piezoelectric/electrostrictive device 20 acan be greatly reduced, and the number of steps for assembling theconstruction components can be reduced, thereby leading to largereduction of costs.

Further, in the eighth piezoelectric/electrostrictive device 20 a, sincethe number of construction components is extremely small and the numberof bonding sites between the construction components is extremely small,there is little or no variation in the adhesion between the constructioncomponents, whereby the eighth piezoelectric/electrostrictive device 20a has device characteristics in which the set precision is high.

Further, in forming the eighth piezoelectric/electrostrictive device 20a, there is no need to adopt means for cutting a device master atnumerous sites as in the prior art, so that there is no contaminationcaused by adhesion of dusts and other contaminants generated at the timeof cutting the device master. For this reason, if base 21 andpiezoelectric/electrostrictive elements 22 a, 22 b are cleaned inadvance in assembling the eighth piezoelectric/electrostrictive device20 a, the assembled piezoelectric/electrostrictive device 20 a haslittle or no contamination, thereby providing a great advantage that thestep of cleaning the piezoelectric/electrostrictive device 20 a can beomitted or carried out in a simple manner.

The mounting of the component to be controlled and others onto theeighth piezoelectric/electrostrictive device 20 a is carried out byfixing them onto the inner surfaces 21 a 1, 21 b 1 on the tip end sideof movable parts 21 a, 21 b via an adhesive. In this case, as will beclear if reference is made to FIG. 19 illustrating a later-mentionedpiezoelectric/electrostrictive device 20 c which is a modification ofthe piezoelectric/electrostrictive device 20 a, if the height H1 ofdevice 20 a is smaller than the height H2 of the component to becontrolled, the height H3 in the state in which device 20 a and thecomponent to be controlled are assembled will be equal to the height H2of the component to be controlled (H3=H2), whereby the height H1 ofdevice 20 a can be ignored. This provides an advantage that a furtherreduction of space can be achieved as compared with thepiezoelectric/electrostrictive devices according to other embodiments ofthe present invention.

Here, in this assembled structure, since the component to be controlledis sandwiched between the two movable parts 21 a, 21 b, the intervalbetween the inner surfaces 21 a 1, 21 b 1 on the tip end side of movableparts 21 a, 21 b must be set substantially equal to the width dimensionincluding the width of the component to be controlled and the thicknessof the intervening adhesive layer. If this is neglected, when theinterval between the inner surfaces 21 a 1, 21 b 1 on the tip end sideof movable parts 21 a, 21 b is too narrow, the component cannot beplaced between the inner surfaces 21 a 1, 21 b 1 on the tip end side ofmovable parts 21 a, 21 b, thereby making the assemblage impossible,whereas if the interval between the inner surfaces 21 a 1, 21 b 1 on thetip end side of movable parts 21 a, 21 b is too wide, the component tobe controlled cannot be bonded to both of the inner surfaces 21 a 1, 21b 1 on the tip end side of movable parts 21 a, 21 b, thereby making theassemblage impossible.

Further, if this assembled structure is adopted, even if the intervalbetween the inner surfaces 21 a 1, 21 b 1 on the tip end side of movableparts 21 a, 21 b is set to be at a width dimension such that thecomponent can be placed and bonded to both of the inner surfaces 21 a 1,21 b 1 on the tip end side of movable parts 21 a, 21 b, if the thicknessof the adhesive layer for bonding the component to be controlled ontothe inner surfaces 21 a 1, 21 b 1 on the tip end side of movable parts21 a, 21 b varies, the displacement resonance of the two movable parts21 a, 21 b is changed, thereby causing variation in the devicecharacteristics. For this reason, in a bending process for forming base21, a press-molding means of high precision is adopted to enable massproduction of bases 21 bent in a highly precise manner. This will reducethe variation in the thickness of the adhesive layer for bonding thecomponent onto the inner surfaces 21 a 1, 21 b 1 on the tip end side ofmovable parts 21 a, 21 b as much as possible, whereby the device willhave a quality with extremely reduced variation of devicecharacteristics.

FIG. 19 illustrates a piezoelectric/electrostrictive device 20 c whichis a first modification of the eighth piezoelectric/electrostrictivedevice 20 a. The piezoelectric/electrostrictive device 20 c has the samebasic construction as the piezoelectric/electrostrictive device 20 a,and is different in construction from the piezoelectric/electrostrictivedevice 20 a only in that the tip ends of movable parts 21 a, 21 b areinwardly bent. Namely, movable parts 21 a, 21 b have bent portions 21 a2, 21 b 2 at the tip ends thereof. The bent portions 21 a 2, 21 b 2 areformed by bending the tip ends of movable parts 21 a, 21 b inwardly byabout 180°, and the inside surfaces of the bent portions 21 a 2, 21 b 2face each other to provide mounting sites for mounting the component Hto be controlled. The component H to be controlled is mounted by beingbonded to the inside surfaces of bent portions 21 a 2, 21 b 2 via asuitable adhesive.

Here, since the other parts of piezoelectric/electrostrictive device 20c are the same as those of piezoelectric/electrostrictive device 20 a,like constituent members and like constituent sites are denoted withlike reference numerals, and their detailed description will be omitted.

Thus, in the piezoelectric/electrostrictive device 20 c, the bondinglength and the bonding area to the component H to be controlled can bedefined by the two bent portions 21 a 2, 21 b 2, thereby effectivelyeliminating the variation of the bonding length and the bonding area tothe component H to be controlled among individual devices. This caneliminate the variation in the value of displacement resonance amongindividual devices caused by the variation in the bonding length and thebonding area to the component H to be controlled.

Here, in the piezoelectric/electrostrictive device 20 c, as described inthe function and effects of the eighth piezoelectric/electrostrictivedevice 20 a, since the height H1 of device 20 c is smaller than theheight H2 of the component to be controlled, the height H3 in the statein which the component H to be controlled is mounted on device 20 c isequal to the height H2 of the component H to be controlled (H3=H2), sothat the height H1 of device 20 c can be ignored, thereby providing anadvantage of further reduction in the space as compared with thepiezoelectric/electrostrictive devices according to other embodiments ofthe present invention.

FIG. 20 illustrates a piezoelectric/electrostrictive device 20 d whichis a second modification of the eighth piezoelectric/electrostrictivedevice 20 a. The piezoelectric/electrostrictive device 20 d has the samebasic construction as the piezoelectric/electrostrictive device 20 a,and is different in construction from the piezoelectric/electrostrictivedevice 20 a only in that the movable parts 21 a, 21 b are formed to benarrow band-shaped plates with steps, and the tip ends of movable parts21 a, 21 b constitute crooked portions 21 a 3, 21 b 3 that are slightlybiased inwardly from the principal part. The crooked portions 21 a 3, 21b 3 of movable parts 21 a, 21 b are positioned to face each other, andthe inside surfaces of these crooked portions 21 a 3, 21 b 3 constitutemounting sites for mounting the component H to be controlled, in thesame manner as the bent portions 21 a 2, 21 b 2 inpiezoelectric/electrostrictive device 20 c. The component H to becontrolled is bonded onto the inside surfaces of crooked portions 21 a3, 21 b 3 via a suitable adhesive. Therefore, thepiezoelectric/electrostrictive device 20 d functions in the same manneras the piezoelectric/electrostrictive device 20 c, and produces the sameactions and effects as the piezoelectric/electrostrictive device 20 c.

Here, since the other parts of piezoelectric/electrostrictive device 20d are the same as those of piezoelectric/electrostrictive device 20 c,the same constituent members and the same constituent sites as inpiezoelectric/electrostrictive device 20 c are denoted with the samereference numerals as in piezoelectric/electrostrictive device 20 c, andtheir detailed description will be omitted.

The ninth piezoelectric/electrostrictive device 20 b shown in FIG. 11belongs to the category of the piezoelectric/electrostrictive device ofthe second form according to the present invention. The ninthpiezoelectric/electrostrictive device 20 b has a base constructed in agreatly different manner from that of the firstpiezoelectric/electrostrictive device 10 a.

Now, referring to FIG. 22B, the ninth piezoelectric/electrostrictivedevice 20 b is made of a base 23 and a pair ofpiezoelectric/electrostrictive elements 22 a, 22 b. Base 23 isconstructed with a pair of right and left long and narrow plate-shapedmovable parts 23 a, 23 b, a flat and narrow plate-shaped fixing part 23c that connects the movable parts 23 a, 23 b with each other at one endthereof, and a flat and narrow plate-shaped mounting part 23 d thatconnects the movable parts 23 a, 23 b with each other at the other endthereof.

Referring to FIG. 21A, the original plate 23A of base 23 is formed bysubjecting a flat plate to a stamping process, and is provided with agenerally square-shaped opening 23 e. Base 23 is formed byperpendicularly bending the right and left sides of original plate 23Aat the opening peripheries of opening 23 e along central lines L1, L2that extend along the opening peripheries in the longitudinal direction,as shown in FIG. 21B. By bending the right and left sides of originalplate 23A in such a manner, the sides of the opening peripheries areformed into movable parts 23 a, 23 b, and the sites between the sides ofthe opening peripheries are formed into fixing part 23 c and mountingpart 23 d.

In base 23 thus integrally constructed from original plate 23A,piezoelectric/electrostrictive elements 22 a, 22 b are bonded via anadhesive onto the outer sides of movable parts 23 a, 23 b as shown inFIG. 22A to form piezoelectric/electrostrictive device 20 b shown inFIG. 22B. The assembled piezoelectric/electrostrictive device 20 bfunctions in the same manner as the conventionalpiezoelectric/electrostrictive devices of this form. However, since base23 is integrally constructed from one sheet of original plate 23A,piezoelectric/electrostrictive device 20 b produces approximately thesame functions and effects as the first piezoelectric/electrostrictivedevice 10 a and the eighth piezoelectric/electrostrictive device 20 a.

In the ninth piezoelectric/electrostrictive device 20 b, fixing part 23c and mounting part 23 d are small, and the bonding area to the actuatoror the component to be controlled is small. However, if one can adoptmeans for firmly joining the component with a small bonding area, suchas spot welding, the ninth piezoelectric/electrostrictive device 20 bhas no disadvantage. A large fixing part or mounting part acts as asuperfluous weight (mass). In this respect, the ninthpiezoelectric/electrostrictive device 20 b is different from the otherpiezoelectric/electrostrictive devices 10 a to 10 g. Since a superfluousmass is absent, the resonance frequency can be set to be high, therebyproviding an advantage that the actuator can be operated at a higherspeed.

Regarding the piezoelectric/electrostrictive devices 10 a to 10 g, 20 ato 20 d according to the above-described embodiments, in the stampedstructure adopted as an original plate for forming the bases 11 to 18,21, and 23, the openings 11 e to 18 e, 21 d, and 23 e are formed bystamping simultaneously at the time of the stamping process. However,these openings 11 e to 18 e, 21 d, and 23 e of the original plate can beformed by machining the original plate stamped out into a predeterminedshape, using means other than the stamping means, for example, ahole-forming machining means such as laser machining, electric dischargemachining, drill machining, supersonic wave machining, or etching.Regarding the hole-forming machining means, if means other than etchingis used, burrs may be generated at the edge of the machined hole;however, the burrs can be easily removed by an etching process or ablasting process.

Further, the movable parts 11 a, 11 b . . . constituting the bases 11,13 to 18, 21, 23 of the piezoelectric/electrostrictive devices 10 a to10 g, 20 a to 20 d are preferably bent at an angle of about 90° to thefixing parts 11 c . . . and the mounting parts 11 d . . . , and theintersecting angle is within the range of 90°±10°, preferably 90°±5°,more preferably 90°±1°. If the angle of bending the movable parts 11 a,11 b . . . is deviated from 90°, the displacement in the flappingdirection will be large. Here, the above notation . . . is used to meanthat the reference numerals of the other corresponding sites areomitted, and is used to abbreviate the description.

The bases 11 to 18, 21, 23 formed by bending are preferably subjected toa supersonic wave cleaning process using a detergent, an organicsolvent, or the like. With the use of supersonic wave cleaning, thebases are not destroyed even if the power is increased, so thatsupersonic wave cleaning with a large power can remove the contaminationeasily.

Further, the piezoelectric/electrostrictive devices 10 a to 10 g, 20 ato 20 d are constructed in such a manner that the base and thepiezoelectric/electrostrictive elements are formed as separate bodies,and the piezoelectric/electrostrictive elements are bonded to themovable parts of the base. However, in thepiezoelectric/electrostrictive devices according to the presentinvention, a piezoelectric/electrostrictive layer and electrodes can beformed as films by means of sputtering, CVD, MBE, or the like or formedas films by the sol-gel method onto the portions to become the movableparts in the original plate before being formed into the base, or ontothe movable parts of the base, thereby to form thepiezoelectric/electrostrictive elements directly on the base.

The piezoelectric/electrostrictive elements 12 a, 12 b, 22 a, 22 bconstituting the piezoelectric/electrostrictive devices 10 a to 10 g, 20a to 20 d according to the above-described embodiments are each providedwith a piezoelectric/electrostrictive layer and a pair of electrodes forapplying an electric field thereto, and arepiezoelectric/electrostrictive elements of unimorph type, bimorph type,or the like. Among these, piezoelectric/electrostrictive elements ofunimorph type are excellent in the stability of the generatingdisplacement, and are also advantageous for weight reduction, so thatthey are suitable as a construction component ofpiezoelectric/electrostrictive devices.

FIGS. 23 and 24 illustrate several examples ofpiezoelectric/electrostrictive elements 31 to 34 that are suitablyadopted as the piezoelectric/electrostrictive elements 12 a, 12 b, 22 a,22 b constituting the piezoelectric/electrostrictive devices 10 a to 10g, 20 a to 20 d.

Piezoelectric/electrostrictive element 31 shown in FIG. 23A has aone-layer structure in which the piezoelectric/electrostrictive layerconsists of one layer, and is constructed with apiezoelectric/electrostrictive layer 31 a, a pair of lower first andupper second electrodes 31 b, 31 c, and a pair of terminals 31 d, 31 e.Piezoelectric/electrostrictive element 32 shown in FIG. 23B has atwo-layer structure in which the piezoelectric/electrostrictive layerconsists of two layers, and is constructed withpiezoelectric/electrostrictive layers 32 a, 32 b, a first electrode 32 cthat intervenes between the two piezoelectric/electrostrictive layers 32a, 32 b, a second electrode 32 d that surrounds the outer sides of thetwo piezoelectric/electrostrictive layers 32 a, 32 b, and a pair ofterminals 32 e, 32 f.

Piezoelectric/electrostrictive elements 33, 34 shown in FIG. 24 eachhave a four-layer structure in which the piezoelectric/electrostrictivelayer consists of four layers. Piezoelectric/electrostrictive element 33shown in FIG. 24A is constructed with piezoelectric/electrostrictivelayers 33 a, 33 b, 33 c, 33 d, first and second electrodes 33 e, 33 fthat intervene between and surround the fourpiezoelectric/electrostrictive layers 33 a, 33 b, 33 c, 33 d, and a pairof terminals 33 g, 33 h. The piezoelectric/electrostrictive element 34shown in FIG. 24B is different from the piezoelectric/electrostrictiveelement 33 in that the terminals are placed at different sites.Piezoelectric/electrostrictive element 34 is constructed withpiezoelectric/electrostrictive layers 34 a, 34 b, 34 c, 34 d, first andsecond electrodes 34 e, 34 f that intervene between and surround thefour piezoelectric/electrostrictive layers 34 a, 34 b, 34 c, 34 d, and apair of terminals 34 g, 34 h.

These piezoelectric/electrostrictive elements 31 to 34 are suitablyadopted as the piezoelectric/electrostrictive elements 12 a, 12 b, 22 a,22 b of the piezoelectric/electrostrictive devices 10 a to 10 g, 20 a to20 d in accordance with the usage of the piezoelectric/electrostrictivedevices.

In addition to piezoelectric ceramic, one can use electrostrictiveceramic, ferroelectric ceramic, antiferroelectric ceramic, or the likeas well in the piezoelectric/electrostrictive layers constituting thepiezoelectric/electrostrictive elements 31 to 34. However, if thepiezoelectric/electrostrictive device is used for positioning themagnetic head of a hard disk drive or the like purpose, it is preferableto use a material whose striation (distortion) hysteresis is smallbecause the linearity between the displacement amount of the mountingpart and the driving voltage or the output voltage is essential. It ispreferable to use a material having a coercive electric field of at most10 kV/mm.

As a material for forming the piezoelectric/electrostrictive layers, onecan specifically mention lead zirconate, lead titanate, magnesium leadniobate, zinc lead niobate, manganese lead niobate, antimony leadstannate, manganese lead tungstate, cobalt lead niobate, bariumtitanate, bismuth sodium titanate, potassium sodium niobate, strontiumbismuth tantalate, and others, which are used either alone or as asuitable mixture thereof. Particularly, a material containing leadzirconate, lead titanate, or magnesium lead niobate as a majorcomponent, or a material containing bismuth sodium titanate as a majorcomponent is suitable.

The characteristics of the piezoelectric/electrostrictive layers can beadjusted by adding a suitable material to the materials for forming thepiezoelectric/electrostrictive layers. As a material to be added, onecan mention oxides of lanthanum, calcium, strontium, molybdenum,tungsten, barium, niobium, zinc, nickel, manganese, cesium, cadmium,chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth,tin, and others, or materials that eventually become oxides, which areused either alone or as a suitable mixture thereof.

For example, by allowing lanthanum or strontium to be contained in leadzirconate, lead titanate, magnesium lead niobate, or the likeconstituting the major component, there will be provided an advantagethat the coercive electric field or the piezoelectric property can beadjusted. Here, it is preferable to avoid addition of a material thateasily undergoes vitrification, such as silica. This is because amaterial such as silica that easily undergoes vitrification is liable toreact with the piezoelectric/electrostrictive layers at the time ofthermal treatment of the piezoelectric/electrostrictive layers, andchanges their composition to deteriorate the piezoelectric properties.

The electrodes constituting the piezoelectric/electrostrictive elements31 to 34 are preferably made of a metal material that is solid at roomtemperature and e+½ellent in electrical conductivity. As a metalmaterial, one can mention metals such as aluminum, titanium, chromium,iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium,palladium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum,gold, or lead, which are used as a single metal or an alloy of thesemetals. Further, one can use a thermal material obtained by dispersingceramics made of the same materials as or made of different materialsfrom the piezoelectric/electrostrictive layers into these metalmaterials.

Piezoelectric/electrostrictive elements 31 to 34 are preferably formedby integrally baking the piezoelectric/electrostrictive layers and theelectrodes in a mutually laminated state. In this case, as theelectrodes, it is preferable to adopt those made of a high-melting-pointmetal material such as platinum, palladium, or an alloy of these, or anelectrode made of a thermal material which is a mixture of ahigh-melting-point metal material and the materials for forming thepiezoelectric/electrostrictive layers or other ceramic materials. Thethickness of the electrodes preferably has a film shape as thin aspossible because the thickness becomes a factor that affects thedisplacement of the piezoelectric/electrostrictive elements. For thisreason, in order that the electrodes formed by being integrally bakedwith the piezoelectric/electrostrictive layers have a film shape as thinas possible, it is preferable to use the material for forming theelectrodes in a form of a metal paste, for example, a gold resinatepaste, platinum resinate paste, silver resinate paste, or the like.

The thickness of each of the piezoelectric/electrostrictive elements 31to 34 is preferably within a range from 40 μm to 180 μm ifpiezoelectric/electrostrictive elements 31 to 34 are to be used as thepiezoelectric/electrostrictive elements 12 a, 12 b, 22 a, 22 b of thepiezoelectric/electrostrictive device according to each embodiment. Ifthe thickness is below 40 μm, piezoelectric/electrostrictive elements 31to 34 are liable to be broken during the handling, whereas if thethickness exceeds 180 μm, the scale reduction of the device will bedifficult. Further, by allowing the piezoelectric/electrostrictiveelements to have a multi-layer structure such as in thepiezoelectric/electrostrictive elements 33, 34, one can increase theoutput of the piezoelectric/electrostrictive elements to enlarge thedisplacement of the device. Furthermore, by allowing thepiezoelectric/electrostrictive elements to have a multi-layer structure,the rigidity of the device will be improved, thereby advantageouslyraising the resonance frequency of the device to increase the speed ofthe displacement operation of the device.

Piezoelectric/electrostrictive elements 31 to 34 are prepared usingmeans for cutting an original plate of a large area, which is formed bylaminating and baking the piezoelectric/electrostrictive layers and theelectrodes by printing or tape molding, out into a predetermineddimension in a large number with the use of a dicing machine, a slicer,a wire-saw, or the like. Piezoelectric/electrostrictive elements 31 to34 are thinner and have a lower hardness than known ceramic bases, sothat the speed of cutting the original plate can be set to be high,whereby the original plates can be processed in a large mass and at ahigh speed.

Piezoelectric/electrostrictive elements 31 to 34 have a simpleplate-shaped structure and can be easily handled with. Also, since thesurface area is small, the amount of adhering dust is small, and thedust can be easily removed. However, since thepiezoelectric/electrostrictive elements are mainly made of a ceramicmaterial, a suitable cleaning condition must be set in supersonic wavecleaning. In a piezoelectric/electrostrictive element cut out from theoriginal plate, it is preferable to perform a precision cleaningtreatment by US cleaning and then perform a heat treatment at 100° C. to1000° C. in atmospheric air so as to completely remove the moisture andorganic substances that have penetrated into fine pores of the ceramicmaterial.

If the piezoelectric/electrostrictive elements 31 to 34 are to beadopted as the piezoelectric/electrostrictive elements 12 a, 12 b, 22 a,22 b constituting the piezoelectric/electrostrictive devices 10 a to 10g, 20 a to 20 d according to each embodiment, it is preferable to use aresin-series adhesive such as epoxy resin, UV resin, or hot-meltadhesive, or an inorganic adhesive such as glass, cement, solder, orbrazing material as a bonding means to the base of each of thepiezoelectric/electrostrictive elements 31 to 34. Also, a mixture ofresin-series adhesive with metal powder or ceramic powder can be used aswell. The hardness of the adhesive is preferably not less than 80 interms of Shore D hardness.

Here, it is preferable to perform a surface roughening treatment such asblasting, etching, or plating on the surface site of the base where thepiezoelectric/electrostrictive element is to be bonded. By allowing thesurface roughness of the bonding site to be Ra=about 0.1 μm to 5 μm, thebonding area can be enlarged to improve the adhesive strength. In thiscase, the surface of the bonding site on thepiezoelectric/electrostrictive element side is preferably rough as well.If one wishes that the electrodes are not electrically conducted to thebase, the electrodes are not disposed on the surface of thepiezoelectric/electrostrictive layer constituting the lowermost layer.

If solder or brazing material is to be used as the adhesive, it ispreferable to dispose an electrode layer made of a metal material on thesurface of the piezoelectric/electrostrictive element in order toimprove the wettability. The thickness of the adhesive is preferablywithin the range from 1 μm to 50 μm. The thickness of the adhesive ispreferably small in view of reducing variations in the displacement andin the resonance characteristics of the device and in view of savingspace; however, in order to ensure the characteristics such as thebonding strength, displacement, and resonance, the optimal thickness isset for each adhesive to be adopted.

In bonding the piezoelectric/electrostrictive element to the base, thepiezoelectric/electrostrictive element is bonded to the base so that thepiezoelectric/electrostrictive element completely overlaps the bendingposition of the fixing part while allowing the electrodes of thepiezoelectric/electrostrictive element to be on the side of the fixingpart of the base. The piezoelectric/electrostrictive element ispreferably bonded so as to align with the end of the base on the fixingpart side; however, in order to facilitate the connection between theterminals of the piezoelectric/electrostrictive element and the externalterminals, one may bond the piezoelectric/electrostrictive element toprotrude outward from the end of the base. However, since thepiezoelectric/electrostrictive element is liable to be broken ascompared with the base which is made of metal, one must take care inhandling the piezoelectric/electrostrictive element.

FIG. 25 illustrates an example in which thepiezoelectric/electrostrictive element 34 is adopted as thepiezoelectric/electrostrictive elements 12 a, 12 b in the firstpiezoelectric/electrostrictive device 10 a that belongs to the categoryof the piezoelectric/electrostrictive device of the second formaccording to the present invention. Hereafter, the firstpiezoelectric/electrostrictive device 10 a of this embodiment will beused as a representative example having a basic construction of thepiezoelectric/electrostrictive device according to the presentinvention. The construction and operation as well as functions andeffects of the piezoelectric/electrostrictive device according to thepresent invention will be described in detail with reference to thefirst piezoelectric/electrostrictive device 10 a.

If a part of piezoelectric/electrostrictive element 34 is positioned atthe fixing part 11 c of the base 11 in thepiezoelectric/electrostrictive device 10 a, (1−Lb/La) is preferably atleast 0.4, more preferably from 0.5 to 0.8, where La is the shortestdistance between the boundary to the mounting part 11 d and the boundaryto the fixing part 11 c in the pair of movable parts 11 a, 11 b, and Lbis the shorter one of the distances from the boundary part between themounting part 11 d and the movable parts 11 a, 11 b to either end of theelectrodes 34 e, 34 f of the piezoelectric/electrostrictive element 34,as illustrated in FIG. 26. If this value is less than 0.4, one cannotobtain a large displacement of the device. If this value is within arange from 0.5 to 0.8, compatibility between the displacement and theresonance of the device can be more easily achieved. In this case, onecan adopt a construction in which the piezoelectric/electrostrictiveelement 34 is bonded to only one of the movable parts 11 a, 11 b,thereby providing a more preferable embodiment. Here, the same appliesto the case in which a part of the piezoelectric/electrostrictiveelement 34 is positioned at a part of the mounting part 11 d.

In the piezoelectric/electrostrictive device 10 a, application ofvoltage to the electrodes 34 e, 34 f of the twopiezoelectric/electrostrictive elements 34 is carried out throughterminals 34 g, 34 h. The terminals 34 g, 34 h are positioned in such amanner that the terminal 34 g to one electrode 34 e is formed toward therear of fixing part 11 c, and the terminal 34 h to the other electrode34 f is formed toward the front direction of fixing part 11 c. Eitherone of the terminals 34 g, 34 h can be omitted by being electricallyconducted to base 11 to be grounded commonly with base 11. The width ofthe piezoelectric/electrostrictive element 34 to be bonded need not bethe same as the width of the bonding site of base 11 (bonding site ofmovable parts 11, 11 b), and the difference in width does not raise anyproblem in the functions of the device.

Piezoelectric/electrostrictive device 10 a is formed, for example, tohave a total length of 1.9 mm and a total width of 1.5 mm by formingbase 11 with SUS304 having a plate thickness of 40 μm.Piezoelectric/electrostrictive element 34 adopted aspiezoelectric/electrostrictive elements 12 a, 12 b is a four-layerstructure in which PZT is used. The thickness of one layer of thepiezoelectric/electrostrictive layers 34 a to 34 d is 15 μm. Theelectrodes 34 e, 34 f are made of platinum of 3 μm, and terminals 34 g,34 h are thin films made of gold paste. Thepiezoelectric/electrostrictive elements 34 are bonded onto outer sidesof movable parts 11 a, 11 b via a one-liquid thermosetting epoxy resinadhesive.

In the piezoelectric/electrostrictive device 10 a thus constructed tohave such a size, the displacement of mounting part 11 d was measuredwhen the piezoelectric/electrostrictive element 34 was driven by asinusoidal wave of 1 kHz with a driving voltage of 20±20 V. Thedisplacement was found to be ±1.5 μm. Further, the resonance frequencyshowing the maximum value of the displacement was measured by sweepingthe frequency at sinusoidal wave voltage ±0.5 V, and was found out to be45 kHz.

Next, the operation of the piezoelectric/electrostrictive deviceaccording to the present invention will be described with reference tothe above-described first piezoelectric/electrostrictive device 10 a.

The piezoelectric/electrostrictive device 10 a is in a state shown inFIG. 26 at the time of non-operation when a voltage is not applied topiezoelectric/electrostrictive elements 12 a, 12 b. In this state, thelongitudinal axis m (longitudinal axis of fixing part 11 c) ofpiezoelectric/electrostrictive device 10 a is almost coincident with thecentral axis n of mounting part 11 d. In this state, a sinusoidal waveWb having a predetermined bias voltage Vb is applied to the pair ofelectrodes 34 e, 34 f in one piezoelectric/electrostrictive element 12b, for example, as shown in the waveform diagram of FIG. 27A, and asinusoidal wave Wa having a phase different by approximately 180° fromthat of the aforesaid sinusoidal wave Wb is applied to the pair ofelectrodes 34 e, 34 f in the other piezoelectric/electrostrictiveelement 12 a, for example, as shown in FIG. 27B.

Now, at the stage when for example the maximum voltage is applied to thepair of electrodes 34 e, 34 f in the one piezoelectric/electrostrictiveelement 12 b, the piezoelectric/electrostrictive layers 34 a to 34 d inthe one piezoelectric/electrostrictive element 12 b undergo shrinkingdisplacement in the principal surface direction thereof.

This generates a stress that warps one movable part 11 b in theillustrated right direction (direction shown by arrow A) inpiezoelectric/electrostrictive device 10 a, for example, as shown inFIG. 28. By this stress, movable part 11 b is warped in that direction.In this case, the pair of electrodes 34 e, 34 f in the otherpiezoelectric/electrostrictive element 12 a are in a state in which avoltage is not applied. Therefore, the other movable part 11 a followsthe warp of the one movable part 11 b so as to warp in the samedirection as that of movable part 11 b. As a result of this, movableparts 11 a, 11 b both displace in the illustrated right direction withrespect to the longitudinal axis m of piezoelectric/electrostrictivedevice 10 a. The displacement amount of this displacement changes inaccordance with the maximum value of the voltage applied to each of thepiezoelectric/electrostrictive elements 12 a, 12 b. The larger themaximum value of the voltage is, the larger the displacement amount willbe.

In particular, if a piezoelectric/electrostrictive material having ahigh coercive electric field is adopted as a material for constructingthe piezoelectric/electrostrictive layers 34 a to 34 d constituting thepiezoelectric/electrostrictive element 34, the aforesaid bias voltagemay be adjusted so that the minimum level will be at a slightly negativelevel, as illustrated by waveforms drawn in two-dot chain lines in FIGS.27A and 27B. In this case, by driving the piezoelectric/electrostrictiveelement to which the bias voltage of negative level is applied, forexample, by driving the other piezoelectric/electrostrictive element 12a, for example, a stress is generated in the other movable part 11 a inthe same direction as the warping direction of the one movable part 11b, thereby providing a larger displacement amount of mounting part 11 d.In other words, by using the waveforms shown in two-dot chain lines inFIGS. 27A and 27B, the piezoelectric/electrostrictive elements 12 a, 12b to which the bias voltage of negative level is applied can have afunction of supporting the piezoelectric/electrostrictive element 12 b,12 a acting as a main agent of displacement operation.

Thus, in piezoelectric/electrostrictive device 10 a, a minutedisplacement of piezoelectric/electrostrictive elements 12 a, 12 b isamplified to become a large displacement operation by utilizing the warpof movable parts 11 a, 11 b, and is transmitted to movable parts 11 a,11 b. This makes it possible to displace the mounting part 11 d to alarge extent with respect to the longitudinal axis m ofpiezoelectric/electrostrictive device 10 a.

In the piezoelectric/electrostrictive device 10 a, it is preferable togive the following consideration so as to allow the functions thereof tobe exhibited with more certainty. Namely, in order to ensure thedisplacement operation of mounting part 11 d, the distance Ld by whichthe substantial driving part Lc of piezoelectric/electrostrictiveelements 12 a, 12 b overlaps the fixing part 11 c or mounting part 11 dis preferably not less than a half of the thickness b of movable parts11 a, 11 b. Further, the device is constructed in such a manner that theratio c/d of the distance c between the inner walls of movable parts 11a, 11 b (distance in the X-axis direction) to the width d of movableparts 11 a, 11 b (distance in the Y-axis direction) is from 0.5 to 20.The ratio c/d is preferably from 1 to 15, more preferably from 1 to 10.The defined values of the ratio c/d are based on the knowledge that thedisplacement amount of mounting part 11 d can be increased and thedisplacement in the X-axis-Z-axis plane can be dominantly obtained.

The ratio e/c of the substantial movable length e in movable parts 11 a,11 b having a total length of e0 to the distance c between the innerwalls of movable parts 11 a, 11 b is preferably from 0.5 to 10, morepreferably from 0.5 to 5. The length f1 of the connecting part betweenthe mounting part 11 d and the movable parts 11 a, 11 b (distance in theZ-axis direction) and the length f2 of the connecting part between thefixing part 11 c and the movable parts 11 a, 11 b (distance in theZ-axis direction) are preferably short. By providing a short mountingpart 11 d, the device can have a reduced weight, and the resonancefrequency can be increased. However, in order to ensure the rigidity ofmounting part 11 d in the X-axis direction to make a firm displacement,the ratios f1/b and f2/b to the thickness b of movable parts 11 a, 11 bis preferably at least 2, more preferably at least 5. Further, thedistance e1x from the bending position L1 of base 11 to fixing part 11 cor mounting part 11 d and the distance e1y from L1 to movable part 11 apreferably satisfy (e1x/b)>1 and (e1y/b)>1, more preferably (e1x/b)≧2and (e1y/b)≧2.

It is essential to set the real dimension of the parts of thepiezoelectric/electrostrictive device 10 a in consideration of thebonding area of mounting part 11 d for mounting the component, thebonding area for mounting the fixing part 11 c to another member, thebonding area for mounting the terminals for the electrodes and others,the strength of the whole device, the durability, the necessarydisplacement amount and resonance property, the driving voltage, andothers.

Specifically, for example, the distance c between the inner walls ofmovable parts 11 a, 11 b is preferably from 100 μm to 2000 μm, morepreferably from 200 μm to 1600 μm. The width d of movable parts 11 a, 11b is preferably from 50 μm to 2000 μm, more preferably from 100 μm to500 μm. In order that the flapping displacement, which is a displacementcomponent in the Y-axis direction, may be effectively restrained, thethickness b of movable parts 11 a, 11 b and the width d of movable parts11 a, 11 b satisfy d>b, and the thickness b is preferably from 2 μm to300 μm, more preferably from 10 μm to 80 μm.

The substantial movable length e in movable parts 11 a, 11 b ispreferably from 200 μm to 3000 μm, more preferably from 300 μm to 2000μm. The connecting length f1 between mounting part 11 d and movableparts 11 a, 11 b and the connecting length f2 between fixing part 11 cand movable parts 11 a, 11 b are preferably from 50 μm to 2000 μm, morepreferably from 100 μm to 1000 μm.

The distance e1x from the bending position L1 of base 11 to fixing part11 c or mounting part 11 d is preferably from 1 μm to 300 μm, morepreferably from 5 μm to 80 μm. Further, the distance e1 y from thebending position L1 of base 11 to movable part 11 a is preferably from 1μm to 1000 μm, more preferably from 5 μm to 500 μm. Here, the distancefrom the bending position L2 of base 11 to fixing part 11 c or mountingpart 11 d (distance corresponding to distance e1 x) and the distancefrom the bending position L2 of base 11 to movable part 11 a (distancecorresponding to distance e1 y) are similar to distance e1 x anddistance e1 y.

By constructing the piezoelectric/electrostrictive device 10 a in such amanner, the displacement in the Y-axis direction can be prevented fromexceeding 10% of the displacement in the X-axis direction. However, bysuitably setting the dimension ratios and the real dimensions within theaforesaid ranges, the device can be driven at a low voltage, and itproduces an excellent effect that the displacement in the Y-axisdirection can be restrained to be not more than 5% of the displacementin the X-axis direction. In other words, mounting part 11 d displacessubstantially in one axial direction, i.e. the X-axis direction, therebyproviding an excellent property that the high-speed response isexcellent and a large displacement is obtained at a low voltage.

Further, in the piezoelectric/electrostrictive device 10 a, base 11constituting the principal construction component has a specific shape,and the movable parts 11 a, 11 b are approximately perpendicular tofixing part 11 c and mounting part 11 d to function as ribs, so that therigidity of the device in the Y-axis direction can be set high. For thisreason, in the piezoelectric/electrostrictive device 10 a, the operationof mounting part 11 d can be selectively generated in a plane (inX-axis-Z-axis plane) alone, and the operation of mounting part 11 d inthe Y-axis-Z-axis plane, i.e. operation in the so-called flappingdirection, can be restrained.

Here, in the device according to the present invention, by devising theshapes of the fixing part and the mounting part of the base, the gimbalof the suspension of the hard disk drive can be integrated with the baseof the device.

Here, FIGS. 29 and 30 illustrate two modifications of the firstpiezoelectric/electrostrictive device 10 a. Thepiezoelectric/electrostrictive devices 10 a 1, 10 a 2 according to thesemodifications have basically the same construction as the firstpiezoelectric/electrostrictive device 10 a. However, in thepiezoelectric/electrostrictive device 10 a 1, circular recesses 11 c 1,11 d 1 are formed by press-molding generally at the central parts offixing part 11 c and mounting part 11 d of base 11. In thepiezoelectric/electrostrictive device 10 a 2, circular through-holes 11c 2, 11 d 2 are formed by stamping generally at the central parts offixing part 11 c and mounting part 11 d of base 11.

In piezoelectric/electrostrictive device 10 a 1, circular recesses 11 c1, 11 d 1 disposed in the fixing part 11 c and mounting part 11 d ofbase 11 serve to accommodate an adhesive for bonding the component to bemounted to fixing part 11 c and mounting part 11 d, whereby the adhesiveaccommodated in the recesses 11 c 1, 11 d 1 increases the bondingstrength to the component and the squeeze-out of the adhesive from thebonding site can be prevented.

Further, in piezoelectric/electrostrictive device 10 a 2, circularthrough-holes 11 c 2, 11 d 2 disposed in the fixing part 11 c andmounting part 11 d of base 11 act as a standard for positioning inassembling (bonding) the component onto fixing part 11 c and mountingpart 11 d, whereby the precision of assembling in later steps can beimproved, and the yield of the products can be improved.

The tenth piezoelectric/electrostrictive device 20 e and the eleventhpiezoelectric/electrostrictive device 20 f shown in FIGS. 1J and 1K arepiezoelectric/electrostrictive devices belonging to the category of thepiezoelectric/electrostrictive device of the third form according to thepresent invention. Referring to FIGS. 31 and 32, thesepiezoelectric/electrostrictive devices 20 e, 20 f each have a basicconstruction including a base having a pair of right and left movableparts, a fixing part that connects the two movable parts with each otherat one end thereof, a mounting part that is separate from the fixingpart and connects the two movable parts with each other at the other endthereof, and a connecting part that is integral with the mounting partand surrounds the mounting part, the movable parts, and the fixing part,as well as a piezoelectric/electrostrictive element disposed on at leastone side of the two movable parts of the base. Thepiezoelectric/electrostrictive devices 20 e, 20 f are largely differentin the construction of the base from the piezoelectric/electrostrictivedevices of the other embodiments.

The base 24 constituting the tenth piezoelectric/electrostrictive device20 e shown in FIG. 31 includes a pair of right and left movable parts 24a, 24 b, a fixing part 24 c that connects the two movable parts 24 a, 24b with each other at one end thereof, a mounting part 24 d that connectsthe two movable parts 24 a, 24 b with each other at the other endthereof, and a connecting part 24 e that is integral with the mountingpart 24 d.

The base 24 has such a configuration that a connecting part is added tothe base 18 constituting the seventh piezoelectric/electrostrictivedevice 10 g. The connecting part 24 e of base 24 has a flat plate shapehaving a square-shaped opening 24 f 1 at the central part thereof, wheremovable parts 24 a, 24 b, fixing part 24 c, and mounting part 24 d areplaced in an integral state in the opening 24 f 1. The connecting part24 e surrounds the principal construction parts of base 24, and the twoside peripheries 24 e 1, 24 e 2 of connecting part 24 e have a springfunction.

Referring to FIG. 32A, the original plate 24A of base 24 has arectangular opening 24 f 1 that will constitute the connecting part 24 eand a gate-shaped opening 24 f 2 that will integrally constitute themovable parts 24 a, 24 b, fixing part 24 c, and mounting part 24 d. Base24 shown in FIG. 32B is formed by bending the original plate 24A alongtwo-dot chain lines L1, L2 shown in FIG. 32A. In the base 24 thusformed, piezoelectric/electrostrictive elements 22 a, 22 b are bondedonto the outer sides of movable parts 24 a, 24 b to form the tenthpiezoelectric/electrostrictive device 20 e shown in FIG. 31.

The tenth piezoelectric/electrostrictive device 20 e has the samefunction as the seventh piezoelectric/electrostrictive device 10 g andproduces approximately the same actions and effects as the seventhpiezoelectric/electrostrictive device 10 g. However, since the tenthpiezoelectric/electrostrictive device 20 e in particular integrallyincludes the connecting part 24 e having a spring function, theconnecting part 24 e can be allowed to function as a gimbal of thesuspension constituting the hard disk drive. In other words, the base 24has a function of a gimbal as well.

The base 25 constituting the eleventh piezoelectric/electrostrictivedevice 20 f shown in FIG. 33 includes a pair of right and left movableparts 25 a, 25 b, a fixing part 25 c that connects the two movable parts25 a, 25 b with each other at one end thereof, a mounting part 25 d thatconnects the two movable parts 25 a, 25 b with each other at the otherend thereof, and a connecting part 25 e that is integral with themounting part 25 d.

The base 25 has such a configuration that a connecting part is added tothe base 18 constituting the seventh piezoelectric/electrostrictivedevice 10 g. The connecting part 25 e of base 25 has a flat plate shapehaving a gate-shaped opening 25 f 1 at the central part thereof andhaving a rectangular opening 25 f 2, whose one end is open, on the tipend side thereof, where movable parts 25 a, 25 b, fixing part 25 c, andmounting part 25 d are placed in an integral state in the opening 25 f2. The connecting part 25 e surrounds the principal construction partsof base 25, and the two side peripheries 25 e 1, 25 e 2 outside theconnecting part 25 e as well as the two side peripheries 25 e 3, 25 e 4inside the connecting part 25 e have a spring function.

Referring to FIG. 34A, the original plate 25A of base 25 has agate-shaped opening 25 f 1 and a rectangular opening 25 f 2 that willconstitute the connecting part 25 e and a gate-shaped opening 25 f 3that will integrally constitute the movable parts 25 a, 25 b, fixingpart 25 c, and mounting part 25 d. Base 25 shown in FIG. 34B is formedby bending the original plate 25A along two-dot chain lines L1, L2 shownin FIG. 34A. In the base 25 thus formed, piezoelectric/electrostrictiveelements 22 a, 22 b are bonded onto the outer sides of movable parts 25a, 25 b to form the eleventh piezoelectric/electrostrictive device 20 fshown in FIG. 33.

The eleventh piezoelectric/electrostrictive device 20 f has the samefunction as the seventh piezoelectric/electrostrictive device 10 g andproduces approximately the same actions and effects as the seventhpiezoelectric/electrostrictive device 10 g. However, since the eleventhpiezoelectric/electrostrictive device 20 f in particular integrallyincludes the connecting part 25 e having a spring function, theconnecting part 25 e can be allowed to function as a gimbal of thesuspension constituting the hard disk drive. In other words, the base 25has a function of a gimbal as well. Furthermore, since the eleventhpiezoelectric/electrostrictive device 20 f has a higher spring functionthat the tenth piezoelectric/electrostrictive device 20 e, the functionof a gimbal can be exhibited with more certainty.

FIG. 35 illustrates a hard disk drive 40 having the tenthpiezoelectric/electrostrictive device 20 e, which is apiezoelectric/electrostrictive device of the third form according to thepresent invention, mounted thereon. The hard disk drive 40 is a knownone provided with a suspension. Base 41 has a voice coil 42 and a magnet43 mounted thereon, and the suspension 45 having the tenthpiezoelectric/electrostrictive device 20 e mounted thereon is attachedto an arm 44 disposed on the base 41. Here, the reference numeral 46denotes a magnetic disk.

Now, referring to FIG. 36, the tenth piezoelectric/electrostrictivedevice 20 e has a magnetic head 47 (slider) fixed onto the fixing part24 c of the base 24 via an adhesive, and is fixed by means of spotwelding or the like to the rear side of the suspension 45 on the rearside of the mounting part 24 d side in the connecting part 24 e of thebase 24. In such a mounting structure of the tenthpiezoelectric/electrostrictive device 20 e, the connecting part 24 e ofthe base 24 has a function of a conventional gimbal, thereby providingan advantage that the use of a conventional gimbal can be omitted inmounting the tenth piezoelectric/electrostrictive device 20 e onto thesuspension 45.

Subsequently, a twelfth piezoelectric/electrostrictive device 10 h shownin FIG. 37 will be described. The twelfth piezoelectric/electrostrictivedevice 10 h relates to the modification of the firstpiezoelectric/electrostrictive device 10 a shown in FIG. 2 to FIG. 4,and only a point that the position of arrangement of thepiezoelectric/electrostrictive elements 12 a, 12 b is changed from theouter sides of the movable parts 11 a, 11 b to the inner sides of themovable parts 11 a, 11 b is different from the firstpiezoelectric/electrostrictive device 10 a.

In other words, the twelfth piezoelectric/electrostrictive device 10 hincludes:

-   -   a base 11 being constructed with one sheet of flat plate, the        base 11 having the fixing part 11 c of a flat plate shape, the        mounting part 11 d that is separated from the fixing part 11 c        and having a flat plate shape, and the pair of left and right        movable parts 11 a, 11 b, the pair of movable parts 11 a, 11 b        each being supported at one end side thereof by each side edge        of the fixing part 11 c and at the other end side thereof by        each side edge of the mounting part 11 d, the respective movable        parts being erect by a predetermined height from side edges of        the fixing part 11 c and the mounting part 11 d to face each        other and extend along the side edges of the fixing part 11 c        and the mounting part 11 d, and    -   piezoelectric/electrostrictive elements 12 a, 12 b arranged on        at least one of inner sides of the pair of left and right        movable parts 11 a, 11 b.

The twelfth piezoelectric/electrostrictive device 10 h may be formed,for example, by forming the movable parts 11 a, 11 b by bending theoriginal plate 11A shown in FIG. 3A to a right angle along two chaindouble-dashed lines L1, L2 as shown in FIG. 3B, and then bonding thepiezoelectric/electrostrictive elements 12 a, 12 b to the inner sides ofthe movable parts 11 a, 11 b with adhesive agent.

Alternatively, the twelfth piezoelectric/electrostrictive device 10 hcan be formed also by bonding the piezoelectric/electrostrictiveelements 12 a, 12 b to “portions which become inner sides of the movableparts 11 a, 11 b later” (side edge portions of the side grooves 11 e 1,11 e 2) of the original plate 11A as shown in FIG. 38A and FIG. 38Brespectively with adhesive agent, and then bending the original plate11A at a right angle along the chain double-dashed lines L1, L2.

The twelfth piezoelectric/electrostrictive device 10 h has followingadvantages. Firstly, since the piezoelectric/electrostrictive elementdoes not exist on the outer sides of the movable parts 11 a, 11 b,destruction of the piezoelectric/electrostrictive element due to contactwith foreign substances from the outside can hardly occur, and hencereliability of the piezoelectric/electrostrictive device is high.

Secondly, since the piezoelectric/electrostrictive element does notexist on the outer sides of the movable parts 11 a, 11 b, an externalsize of the piezoelectric/electrostrictive device 10 h is reduced, andhence a space required for mounting the piezoelectric/electrostrictivedevice 10 h can be reduced.

Thirdly, as shown in FIG. 38A and FIG. 38B, in a case where the originalplate 11A is bent after having bonded the piezoelectric/electrostrictiveelements 12 a, 12 b to the original plate 11A, since thepiezoelectric/electrostrictive element does not exist on “portions whichbecome outer sides of the movable parts 11 a, 11 b later”, the originalplate 11A can be bent by applying a force to the “portions which becomethe outer sides of the movable parts 11 a, 11 b later”. Therefore,protection of the piezoelectric/electrostrictive element which isrequired when performing the bending process can be simplified.

Subsequently, a thirteenth piezoelectric/electrostrictive device 10 ishown in FIG. 39 will be described. The thirteenthpiezoelectric/electrostrictive device 10 i further includes thepiezoelectric/electrostrictive elements 12 a, 12 b disposed on the outersides of the movable parts 11 a, 11 b of the twelfthpiezoelectric/electrostrictive device 10 h shown in FIG. 37.

The thirteenth piezoelectric/electrostrictive device 10 i can be formed,for example, by forming the movable parts 11 a, 11 b by bending theoriginal plate 11A shown in FIG. 3A at a right angle along the chaindouble-dashed lines L1, L2 as sown in FIG. 3B, and then bonding thepiezoelectric/electrostrictive elements 12 a to the inner and outersides of the movable part 11 a respectively with adhesive agent andbonding the piezoelectric/electrostrictive elements 12 b to the innerand outer sides of the movable part 11 b respectively with adhesiveagent.

Alternatively, the thirteenth piezoelectric/electrostrictive device 10 imay also be formed by bonding the piezoelectric/electrostrictiveelements 12 a, 12 b to the “portions which become the inner sides of themovable parts 11 a, 11 b later” of the original plate 11A as shown inFIG. 38A and 38B respectively with adhesive agent, and then forming themovable parts 11 a, 11 b by bending the original plate 11A at a rightangle along the chain double-dashed lines L1, L2 and then bonding thepiezoelectric/electrostrictive elements 12 a, 12 b to the outer sides ofthe movable parts 11 a, 11 b with adhesive agent.

Alternatively, the thirteenth piezoelectric/electrostrictive device 10 imay also be formed by bonding the piezoelectric/electrostrictiveelements 12 a, 12 b to the “portions which become the outer sides of themovable parts 11 a, 11 b later” of the original plate 11A with adhesiveagent, as shown in FIG. 40A and FIG. 40B, then bending the originalplate 11A at a right angle along the chain double-dashed lines L1, L2 toform the movable parts 11 a , 11 b as shown in FIG. 41A and FIG. 41B,and then bonding the piezoelectric/electrostrictive elements 12 a, 12 bon the inner sides of the movable parts 11 a, 11 b with adhesive agent.

The thirteenth piezoelectric/electrostrictive device 10 i has followingadvantages. Firstly, since the total driving force of thepiezoelectric/electrostrictive elements is increased, displacement ofthe movable parts 11 a, 11 b (therefore, non-controlled part H) can beincreased.

Secondly, the resonant frequency of the piezoelectric/electrostrictivedevice can be increased.

Thirdly, the non-controlled part H can be driven efficiently by applyingthe same reference drive signal to the piezoelectric/electrostrictiveelement 12 a on the outer side of the movable part 11 a and thepiezoelectric/electrostrictive element 12 b on the inner side of themovable part 11 b, and applying the drive signals whose phase is shiftedfrom the reference drive signal by 180° to thepiezoelectric/electrostrictive element 12 a on the inner side of themovable part 11 a and the piezoelectric/electrostrictive element 12 b onthe outer side of the movable part 11 b.

Subsequently, a fourteenth piezoelectric/electrostrictive device 40 ashown in FIG. 42 will be described. In the above-describedpiezoelectric/electrostrictive device, long and narrow plate-shapedpiezoelectric/electrostrictive elements are disposed on the sidesurfaces of the movable part which are erect perpendicularly from theflat surface of the base. In other words, the long and narrowplate-shaped piezoelectric/electrostrictive element is arrangedperpendicularly with respect to the flat surface of the base. On theother hand, a characteristic of the fourteenthpiezoelectric/electrostrictive device 40 a is in that the long andnarrow plate-shaped piezoelectric/electrostrictive elements are disposedhorizontally with respect to the flat surface of the base.

Specifically, the fourteenth piezoelectric/electrostrictive device 40 aincludes: a base 41 being constructed with one sheet of flat plate, thebase 41 having a fixing part 41 c of a flat plate shape, a mounting part41 d that is separate from the fixing part 41 c and having a flat plateshape, and a pair of left and right movable parts 41 a, 41 b, the pairof movable parts 41 a, 41 b each being supported at one end side thereofby each side edge of the fixing part 41 c and at the other end sidethereof by each side edge of the mounting part 41 d, the respectivemovable parts being erect by a predetermined height from side edges ofthe fixing part 41 c and the mounting part 41 d to face each other andextend along the side edges of the fixing part 41 c and the mountingpart 41 d, and

first receiving parts 41 e, 41 f extending from a mid portion betweenthe one end side and the other end side of at least one of the pair ofleft and right movable parts 41 a, 41 b in parallel with the flatsurface of the base 41,

second receiving parts 41 g, 41 h extending from at least one of theside edges of the fixing part 41 c in parallel with the flat surface ofthe base 41, and

piezoelectric/electrostrictive elements 42 a, 42 b disposed at one endside thereof on the second receiving parts 41 g, 41 h and at the otherend side thereof on the first receiving parts 41 e, 41 f so as toconnect the first receiving parts 41 e, 41 f and the second receivingparts 41 g, 41 h.

The base 41 of the fourteenth piezoelectric/electrostrictive device 40 ais formed from an original plate 41A shown in FIG. 43A. The originalplate 41A is a punched structure formed by stamping a flexible flatplate which can be bent, and is formed into a shape of the base 41extended into a planar state. The flat plate for forming the originalplate 41A is preferably metal in terms of strength.

The original plate 41A is formed with an H-shaped opening 41 i and apair of left and right slits 41 j 1, 41 j 2. The opening 41 i and theslits 41 j 1, 41 j 2 are formed simultaneously at the time of stampingthe flat plate. The slits 41 j 1, 41 j 2 are provided for dividing“portions which become the movable parts 41 a, 41 b later and “portionswhich become second receiving parts 41 g, 41 h later”.

The opening 41 i includes a rectangular shaped front opening 41 i 1formed on one end side (front end side) at the center of the originalplate 41A, a rectangular shaped rear opening 41 i 2 formed on the otherend side (rear end side) at the center thereof, and a rectangular shapedcenter opening 41 i 3 which connects the front opening 41 i 1 and therear opening 41 i 2 with each other at the center of the original plate41A.

The base 41 is formed by bending the original plate 41A at a right anglealong dashed lines L1, L2 to form the movable parts 41 a, 41 b as shownin FIG. 43A and FIG. 43B, and then bending the original plate 41A at aright angle along dashed lines L3, L4 to form the first receiving parts41 e, 41 f.

Accordingly, the first receiving parts 41 e, 41 f extend outward inparallel with the flat surface of the base 41. The second receivingparts 41 g, 41 h also extend from the side edge of the fixing part 41 coutward in parallel with the flat surface of the base 41 without beingbent. Consequently, the thin plate shaped first receiving parts 41 e, 41f and the thin plate shaped second receiving parts 41 g, 41 h exist onthe identical plane (on a plane of the base 41 including the fixing part41 c and the mounting part 41 d).

The fourteenth piezoelectric/electrostrictive device 40 a is formed bybonding the other end and one end of the piezoelectric/electrostrictiveelement 42 a on upper surfaces of the first receiving part 41 e and thesecond receiving part 41 g respectively with adhesive agent so as toconnect the first receiving part 41 e and the second receiving part 41 gof the base 41 thus formed, and bonding the other end and one end of thepiezoelectric/electrostrictive element 42 b on upper surfaces of thefirst receiving part 41 f and the second receiving part 41 hrespectively with adhesive agent so as to connect the first receivingpart 41 f and the second receiving part 41 h. Accordingly, the long andnarrow shaped piezoelectric/electrostrictive elements 42 a, 42 b arearranged in parallel with the flat surface of the base 41.

The fourteenth piezoelectric/electrostrictive device 40 a has followingadvantages. Firstly, as a piezoelectric/electrostrictive device 40 baccording to a first modification of the fourteenthpiezoelectric/electrostrictive device 40 a shown in FIG. 44, byenlarging the length of extension of first receiving parts 43 e, 43 fand second receiving parts 43 g, 43 h in the lateral direction,piezoelectric/electrostrictive elements 44 a, 44 b of large width can beused. Consequently, the drive force of thepiezoelectric/electrostrictive element can be increased, and hencedisplacement of movable parts 43 a, 43 b (therefore the non-controlledpart H) can be increased.

Secondly, since the piezoelectric/electrostrictive elements 44 a, 44 bof large width can be used as described above, handling of thepiezoelectric/electrostrictive elements is facilitated.

Thirdly, by providing expandable structure (arcuate curved portions 45 a1, 45 b 1 in top view in FIG. 45, bent portions 47 a 1, 47 b 1 ofrectangular shape in top view in FIG. 46, and bent portions 48 a 1, 48 b1 of triangular shape in top view in FIG. 47) at a portion between thefirst receiving part and the second receiving part of the long andnarrow plate shaped movable portions as piezoelectric/electrostrictivedevices 40 c-40 e according to second to fourth modifications of thefourteenth piezoelectric/electrostrictive device 40 a shown in FIG. 45to FIG. 47, expansion and contraction of thepiezoelectric/electrostrictive elements can be converted intodisplacement of the movable part (therefore the non-controlled part H)efficiently.

Fourthly, since the piezoelectric/electrostrictive element is arrangedperpendicularly with respect to the movable part, impact resistantproperty of the piezoelectric/electrostrictive element is enhanced.

Subsequently, a fifteenth piezoelectric/electrostrictive device 50 ashown in FIG. 50 will be described. In the above-describedpiezoelectric/electrostrictive device, thepiezoelectric/electrostrictive element formed mainly of PZT is directlyadhered to a metallic base. On the other hand, the characteristic of thefifteenth piezoelectric/electrostrictive device 50 a is in that thepiezoelectric/electrostrictive element formed mainly of PZT is bonded toa reinforcing member (actuator) formed mainly of zirconia, and thereinforcing member is bonded to the metallic base.

A method of manufacturing the fifteenth piezoelectric/electrostrictivedevice 50 a will be described below. As shown in FIG. 48, firstly, longand narrow plate-shaped piezoelectric/electrostrictive elements 52 a, 52b formed of PZT of the fifteenth piezoelectric/electrostrictive device50 a are bonded to outer sides of thin plate parts of a reinforcingmember 51 being formed of zirconia and having a pair of left and rightthin plate parts, and a fixing part for supporting the respective thinplate parts with adhesive agent. Then, adhesive agent is applied to apredetermined range (see a hatched range) on the upper surface of thefixing part 11 c of the base 11 shown in FIG. 3B.

Subsequently, as shown in FIG. 49, the fixing part of the reinforcingmember 51 which is integral with the piezoelectric/electrostrictiveelements 52 a, 52 b is placed on the upper surface of the fixing part 11c of the base 11 so that the inner sides of the thin plate parts of thereinforcing member 51 face the outer sides of the movable parts 11 a, 11b of the base 11. Accordingly, the reinforcing member 51 which isintegral with the piezoelectric/electrostrictive elements 52 a, 52 b isbonded and integrated with the base 11 by the adhesive agent applied onthe upper surface of the fixing part 11 c of the base 11.

At the last, as shown in FIG. 50, resin g is injected into a portionformed with a gap between the movable parts 11 a, 11 b of the base 11and the reinforcing member 51 to achieve resin adhesion, whereby thefifteenth piezoelectric/electrostrictive device 50 a is formed.

A piezoelectric/electrostrictive device 50 b according to a firstmodification of the piezoelectric/electrostrictive device 50 a shown inFIG. 51 and FIG. 52 is different from the fifteenthpiezoelectric/electrostrictive device 50 a in that reinforcing members53 a, 53 b formed of a pair of left and right long and narrowplate-shaped zirconia are used as the reinforcing members (actuator).

In other words, as shown in FIG. 51, in thepiezoelectric/electrostrictive device 50 b, the long and narrowplate-shaped piezoelectric/electrostrictive elements 52 a, 52 b arebonded to one side surfaces of the reinforcing members 53 a, 53 b, andas shown in FIG. 52, the other surfaces of the reinforcing members 53 a,53 b are bonded to the outer sides of the movable parts 11 a, 11 b ofthe base 11.

A piezoelectric/electrostrictive device 50 c according to a secondmodification of the fifteenth piezoelectric/electrostrictive device 50 ashown in FIG. 53 and FIG. 54 is different from thepiezoelectric/electrostrictive device 50 b in that a pair of left andright reinforcing members 54 a, 54 b formed of long and narrowplate-shaped zirconia each formed with a hook-shaped portion at one endthereof are used as the reinforcing members (actuators).

As shown in FIG. 54, in the piezoelectric/electrostrictive device 50 c,the reinforcing members 54 a, 54 b having thepiezoelectric/electrostrictive elements 52 a, 52 b adhered thereon arebonded and fixed to the base 11 so that inner sides of the hook-shapedportions come into tight contact with the one side surfaces of themovable parts 11 a, 11 b (front side) of the base 11.

A piezoelectric/electrostrictive device 50 d according to a thirdmodification of the fifteenth piezoelectric/electrostrictive device 50 ashown in FIG. 55 is different from the piezoelectric/electrostrictivedevice 50 c in that reinforcing member 55 a, 55 b formed of a pair ofleft and right long and narrow plate-shaped zirconia each formed with ahook-shaped portion also on the other end in addition to the one end areused as the reinforcing members (actuators).

As shown in FIG. 55, in the piezoelectric/electrostrictive device 50 d,the reinforcing members 55 a, 55 b having thepiezoelectric/electrostrictive elements 52 a, 52 b bonded thereon arebonded and fixed to the base 11 so that the inner sides of thehook-shaped portions on one end come into tight contact with the sidesurfaces of the movable parts 11 a, 11 b on one end of the base 11, andthe inner sides of the hook-shaped portions on the other end come intotight contact with the side surfaces of the movable parts 11 a, 11 b onthe other end of the base 11. The piezoelectric/electrostrictiveelements 52 a, 52 b are extended from one end portions (front endportions) on the outer sides of the reinforcing members 55 a, 55 b toportions corresponding to the substantially half the length of thelength of the reinforcing members 55 a, 55 b in the fore-and-aftdirection.

A piezoelectric/electrostrictive device 50 e according to a fourthmodification of the fifteenth piezoelectric/electrostrictive device 50 ashown in FIG. 56 is different from the piezoelectric/electrostrictivedevice 50 d in that in addition to the piezoelectric/electrostrictiveelements 52 a, 52 b extending from the one end portions (front portions)to the portions corresponding to the substantially half the length ofthe reinforcing members 55 a, 55 b in the fore-and-aft direction on theouter sides of the reinforcing members 55 a, 55 b, thepiezoelectric/electrostrictive elements 52 a, 52 b extending from theother end portions (rear end portions) to the portions corresponding tothe substantially half the length in the fore-and-aft direction arebonded on the outer sides of the reinforcing members 55 a, 55 b.

A piezoelectric/electrostrictive device 50 f according to a fifthmodification of the fifteenth piezoelectric/electrostrictive device 50 ashown in FIG. 57 is different from the piezoelectric/electrostrictivedevice 50 e in that piezoelectric/electrostrictive elements 56 a, 56 bextending from the one end portions (front end portions) to the otherend portions (rear end portions) continuously on the outer sides of thereinforcing members 55 a, 55 b.

The fifteenth piezoelectric/electrostrictive device 50 a and thepiezoelectric/electrostrictive devices 50 b-50 f according to themodifications have following advantages. Firstly, although thepiezoelectric/electrostrictive element formed of PZT is easily broken,since stiff reinforcing members formed of zirconia are used forreinforcing the piezoelectric/electrostrictive elements, handling of thepiezoelectric/electrostrictive device is facilitated.

Secondly, by using the hook-shaped portions as described above, thepositions of the reinforcing members with respect to the base(therefore, the positions of the piezoelectric/electrostrictiveelements) can be aligned accurately with intended positions. Therefore,variations in characteristics among the piezoelectric/electrostrictivedevices can be reduced.

Thirdly, by using the hook-shaped portions as described above, assemblyof the reinforcing members with respect to the base is facilitated.

Fourthly, by using the stiff reinforcing member formed of zirconia forreinforcing the piezoelectric/electrostrictive element, impact resistantproperty of the piezoelectric/electrostrictive elements increases.

Fifthly, the resonance frequency of the piezoelectric/electrostrictivedevice can be increased.

Sixthly, as described above, since the positions of thepiezoelectric/electrostrictive elements with respect to the base can bealigned accurately with the intended positions, electrical connectionbetween electrodes in the piezoelectric/electrostrictive element and anexternal drive circuit can be achieved easily.

Seventhly, since the reinforcing member can be upsized, assembly of thereinforcing member to the base is facilitated.

Eighthly, since flexibility in shape of the reinforcing member such aswidth or height is high, modification in design for achieving intendedcharacteristics and functions is facilitated.

For example, if the thickness of the movable parts 11 a, 11 b (thereforethe thickness of the original plate 11A) is small in the firstpiezoelectric/electrostrictive device 10 a shown in FIG. 2 to FIG. 4,when the piezoelectric/electrostrictive elements 12 a, 12 b are driven,there may occur such a phenomenon that displacement of the other endsides of the movable parts 11 a, 11 b (rear end sides, on the side ofthe mounting part 11 d) (therefore, displacement of the non-control partH) is reduced because portions on one end sides of the movable parts 11a, 11 b (front end side, on the side of the fixing part 11 c) aredeformed.

In such a case, as shown in FIG. 58, a reinforcing member RE may beinserted between the respective portions on the one end sides (front endsides, on the side of the fixing part 11 c) of the movable parts 11 a,11 b for reinforcing the same. The reinforcing member RE may be, forexample, of ceramic, metal, or resin. In this example, the reinforcingmember RE assumes a square pole shape. However, the shape is not limitedthereto, and for example, may be a shape of cylindrical column shape.

1. A piezoelectric/electrostrictive device comprising: a base beingconstructed with one sheet of flat plate, the base having a fixing partof a flat plate shape, a mounting part that is separate from the fixingpart and having a flat plate shape, and a pair of left and right movableparts, the pair of movable parts each being supported at one end sidethereof by each side edge of the fixing part and at the other end sidethereof by each side edge of the mounting part, the respective movableparts being erect by a predetermined height from side edges of thefixing part and the mounting part to face each other and extend alongthe side edges of the fixing part and the mounting part, and apiezoelectric/electrostrictive element arranged on an inner side of atleast one of the pair of left and right movable parts.
 2. Apiezoelectric/electrostrictive device according to claim 1, wherein apiezoelectric/electrostrictive element is further provided on an outerside of at least one of the pair of left and right movable parts.
 3. Apiezoelectric/electrostrictive device comprising: a base beingconstructed with one sheet of flat plate, the base having a fixing partof a flat plate shape, a mounting part that is separate from the fixingpart and having a flat plate shape, a pair of left and right movableparts, the pair of movable parts each being supported at one end sidethereof by each side edge of the fixing part and at the other end sidethereof by each side edge of the mounting part, the respective movableparts being erect by a predetermined height from side edges of thefixing part and the mounting part to face each other and extend alongthe side edges of the fixing part and the mounting part, a firstreceiving part extending from a mid portion between the one end side andthe other end side of at least one of the pair of left and right movableparts in parallel with a flat surface of the base, and a secondreceiving part extending from at least one of the side edges of thefixing part in parallel with the flat surface of the base, and apiezoelectric/electrostrictive element disposed at one end side thereofon the second receiving part and at the other end side thereof on thefirst receiving part so as to connect the first receiving part and thesecond receiving part.